JP2011257727A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can perform the same good image formation as that in a recording material having a flat surface, even in the case of low deposition amount image such as a highlight image or a line image in a recessed portion of the recording material such as leather-like paper.SOLUTION: A image forming apparatus includes first control means 30 for generating pixel data which can form a gradation pattern having the same or substantially the same average density as that of a gradation pattern in the case of the recording material having the flat surface according to density of a document image and an uneven state of the surface of the recording material, and light exposure means 3 for irradiating a photoreceptor with light based on the pixel data generated by the first control means 30 to form a latent image in the photoreceptor.

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to an improvement in exposure control when a latent image is formed by irradiating a photoconductor with light.

As a measure to prevent unauthorized copying of printed matter (lithographic printing, letterpress printing, etc.) with a level sufficient for authenticity by visual and tactile printing, it is considered to print on a sheet-shaped recording material such as Lesac paper It is done. When such a printed matter is used as an original and is copied on plain paper or coated paper by an electrophotographic image forming apparatus, the texture is clearly different from the original, so authenticity can be determined.
If a copy is made using the same brand of lazac paper as the printed material, the image area in the relatively low area and the image area in the relatively high area appear to have different image densities. You can see at a glance that it is a copy.
Although it is possible to prevent unauthorized copying in this way, on the other hand, the means for preventing unauthorized copying using a sheet-like recording material having irregularities on the surface of resack paper or the like is a conventional general means. An electrophotographic image forming apparatus cannot be used because it cannot print normally as described above.

As a reason why printing cannot be performed normally, for example, when transferring the toner adhering to the surface of the intermediate transfer belt onto the recording material, if the distance to the recording material surface is long, the toner is difficult to reach only with a DC voltage, This is because white spots and dust are likely to occur.
Therefore, in order to enable printing on a sheet-like recording material having a deep concavo-convex structure such as resack paper or embossed paper, an AC superposition transfer bias type electrophotographic image forming apparatus has been proposed.
In this image forming apparatus, by superimposing an AC voltage on a DC voltage, the toner flies while reciprocating, and as a result, the probability of reaching the surface of the recording material is increased, and white spots and dust are suppressed. (For example, refer to Patent Document 1).

  As another apparatus, a multiple transfer type image forming apparatus is known. This image forming apparatus is configured to transfer toner images of the same color and the same color onto a recording material having deep irregularities in two or more times by a multiple transfer method. This technical means performs uniform and comprehensive control by a probabilistic behavior regardless of the uneven structure on the surface of the recording material and the content of the original image (see, for example, Patent Document 2).

  The present inventor uses a transfer experiment apparatus in which a lazac paper is sandwiched between flat plate electrodes based on Patent Document 1, and the transfer bias is (1) DC, (2) DC + AC, and (3) AC. I tried a transcription experiment. As a result, in the case of solid images, at least in the case of alternating current being applied (2) and (3), the lack of transfer to the recesses on the surface of the resack paper tends to be improved. In the case of a low adhesion amount image such as a line image, it was confirmed that the improvement was insufficient, and it was confirmed that the means disclosed in Patent Document 1 was still insufficient.

  As described above, the technique of Patent Document 2 performs uniform and comprehensive control based on the stochastic behavior regardless of the uneven structure on the surface of the recording material and the content of the original image. As a result, the toner is excessively transferred to other areas. In addition, there is a disadvantage that an image forming process other than fixing increases.

  Accordingly, the present invention provides an image capable of forming a good image similar to a recording material having a flat surface even in the case of a low adhesion amount image such as a highlight image or a line image in a concave portion of a recording material such as a resack paper. It is an object to provide a forming apparatus.

In order to solve the above problems, the image forming apparatus according to the present invention has the following technical means.
The invention according to claim 1 is a gradation pattern that is the same or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the density of the original image and the unevenness of the surface of the recording material. 1st control means for generating pixel data that can be formed, and exposure for irradiating the photoconductor with light based on the pixel data generated by the first control means to form a latent image on the photoconductor And an image forming apparatus.
The invention according to claim 2 is the same as or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the image density of the original and the uneven state of the surface of the recording material. Second control means for adjusting the exposure signal, and exposure means for irradiating the photoconductor with light based on the exposure signal adjusted by the second control means to form a latent image on the photoconductor An image forming apparatus is characterized.
The invention according to claim 3 is the same as or substantially the same as the average density of the gradation pattern in the case of the recording material having a flat surface, depending on the image density of the original and the uneven state of the surface of the recording material. An image comprising a third control means for adjusting the developing bias, and a developing means for developing the latent image formed on the photosensitive member into a toner image by applying the developing bias adjusted by the third control means. Features a forming device.
According to a fourth aspect of the present invention, there is provided a gradation pattern that is the same as or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the density of the original image and the surface roughness of the recording material. Is equal to the average density of the gradation pattern in the case of a recording material having a flat surface, according to the first control means for generating pixel data that can be formed, and the image density of the original and the surface roughness of the recording material Or based on the second control means for adjusting the exposure signal so as to be substantially the same, the pixel data generated by the first control means, and the exposure signal adjusted by the second control means. And an exposure unit that irradiates the photosensitive member with light to form a latent image on the photosensitive member.
The invention according to claim 5 is a gradation pattern that is the same or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the density of the original image and the unevenness of the surface of the recording material. 1st control means for generating pixel data that can be formed, and exposure for irradiating the photoconductor with light based on the pixel data generated by the first control means to form a latent image on the photoconductor The developing bias is adjusted so as to be the same or substantially the same as the average density of the gradation pattern in the case of the recording material having a flat surface, according to the means, the image density of the original, and the unevenness state of the surface of the recording material. An image forming apparatus comprising: a third control unit; and a developing unit that develops a latent image formed on the photosensitive member into a toner image by applying a development bias adjusted by the third control unit. To do.
The invention according to claim 6 is a gradation pattern that is the same or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the density of the original image and the unevenness of the surface of the recording material. Is equal to the average density of the gradation pattern in the case of a recording material having a flat surface, according to the first control means for generating pixel data that can be formed, and the image density of the original and the surface roughness of the recording material Alternatively, the second control means for adjusting the exposure signal so as to be substantially the same, and the gradation pattern in the case of the recording material having a flat surface according to the image density of the original and the unevenness state of the surface of the recording material. Third control means for adjusting the developing bias so as to be the same as or substantially the same as the average density, the pixel data generated by the first control means, and the exposure adjusted by the second control means Based on signal The exposure unit for irradiating the photosensitive member with light to form a latent image on the photosensitive member, and the developing bias adjusted by the third control unit are applied, and the latent image formed on the photosensitive member is converted into toner. The image forming apparatus includes a developing unit that develops an image.
According to a seventh aspect of the present invention, in any one of the first, fourth, fifth, and sixth aspects, the first control means obtains a pattern type from the recording material, or the recording type recording means. Either one or both of the reflection pattern extracting means for extracting the reflection pattern of the material and acquiring information related to the uneven state of the surface of the recording material, and pattern data indicating the uneven state of the surface of the recording material are stored. Pattern data storage means, and pattern data acquisition means for acquiring information relating to the uneven state of the surface of the recording material from the pattern data storage means based on the pattern type acquired by the pattern type acquisition means. It is characterized by that.
The invention according to claim 8 is the encryption pattern data storage means in which the pattern data is encrypted and the encryption pattern data is stored, and the encryption pattern data storage means stores the encryption pattern data. The pattern data obtaining means obtains data, and the decrypting means decrypts the obtained encrypted pattern data.
The invention according to claim 9 includes storage means for storing a decryption key for decrypting the encrypted pattern data according to claim 8, wherein the pattern data acquisition means obtains the decryption key from the storage means. Obtaining and the decrypting means decrypts the encrypted pattern data using the obtained decryption key.

  According to the present invention, even in the case of a low adhesion amount image such as a highlight image or a line image in a concave portion of a recording material such as a resack paper, it is possible to form a good image similar to a recording material having a flat surface. An image forming apparatus can be provided.

1 is a schematic diagram of a main part of an image forming apparatus according to a first embodiment; It is the block diagram which showed the structure of the 1st control means. It is the schematic diagram which illustrated the halftone dot pattern comprised by 4x4 pixel. It is the diagram which showed the conversion function showing the correspondence of the halftone dot pattern before correction | amendment and the halftone dot pattern after correction | amendment in a certain height level. It is a schematic diagram showing an arbitrary gradation using a halftone dot pattern, and (a) is a state diagram before correction in which a halftone dot pattern of the first gradation (# 1) is arranged. (b) State diagram after correction replaced with a halftone dot pattern. FIG. 5 is a diagram showing a conversion function for image level correction at a certain height level in the case of a monochrome 256-tone image. It is a schematic diagram of the recording material with an unevenness | corrugation. It is a schematic diagram of the recording material which has an unevenness | corrugation only in a specific area | region. FIG. 3 is a schematic diagram of a main part of an image forming apparatus according to a second embodiment. FIG. 6 is a block diagram showing a configuration of first control means according to the second exemplary embodiment. It is the block diagram which showed the structure of the 2nd control means concerning Embodiment 3 which a part was abbreviate | omitted. It is the diagram which showed the relationship between a power modulation coefficient and relative depth. It is the block diagram which showed the structure of the 3rd control means concerning Embodiment 4 which a part was abbreviate | omitted. It is a diagram showing the relationship between the height difference feature amount and the development bias coefficient. It is the block diagram which showed the control means concerning Embodiment 5 which combined the 1st-3rd control means.

  Embodiments of an image forming apparatus according to the present invention will be described with reference to the accompanying drawings.

(Embodiment 1)
First, an outline of the image forming apparatus according to the first embodiment will be described.
As shown in FIG. 1, the image forming apparatus according to the first embodiment includes a photosensitive drum 1 that is provided to be rotated clockwise and a toner image is formed, and a toner that is provided around the photosensitive drum 1 and has toner on the photosensitive drum 1. An image forming unit for forming an image, and a plurality of rollers that are rotated in a counterclockwise direction so as to form an inverted triangle, and are arranged so that the photosensitive drum 1 is in contact with the horizontal portion and formed on the photosensitive drum 1 The intermediate transfer belt 7 to which the toner image transferred is transferred, and a roller provided across the intermediate transfer belt 7 so as to face the roller below the center of the plurality of rollers across the intermediate transfer belt 7 and the roller. Transfer means 8 for transferring the toner image transferred to the intermediate transfer belt 7 to a sheet-like recording material P, and applying heat and pressure to the recording material P on which the toner image has been transferred by the transfer means 8 A fixing unit 9 for fixing the toner image to the recording material P; a registration roller 12 for feeding the recording material P to the transfer unit 8 at a predetermined timing; and a recording material P upstream of the registration roller 12. The pattern type detection sensor 10 for detecting the P pattern type, and a series of operations related to image formation, and the uneven state of the recording material P and the density of the original image based on the information detected by the pattern type detection sensor 10 And first control means 30 for executing control in consideration of the above. In addition, the image forming apparatus according to the first embodiment can accept document data from a scanner unit (not shown) or host means 40 (FIG. 2) such as a personal computer.

  The image forming unit cleans the surface of the photosensitive drum 1 by removing the surface of the photosensitive drum 1 in order clockwise from the contact portion between the photosensitive drum 1 and the intermediate transfer belt 7 in the clockwise direction around the photosensitive drum 1. Blade-shaped cleaning means 6 for charging, charging means 2 for charging the surface of the photosensitive drum 1, exposure means 3 for irradiating the surface of the charged photosensitive drum 1 with light based on pixel data to form a latent image, Developing means 4 for developing the image into a toner image is provided.

  Between the pair of rollers constituting the transfer means 8, a transfer bias with a constant amplitude AC voltage or a transfer bias in which a constant amplitude AC voltage is superimposed on a constant DC voltage is applied. For example, an AC transfer bias having a DC component of 0 V, a frequency of 1 kHz, and a peak-to-peak voltage of 1200 V is applied.

Next, an outline of a series of operations of the image forming apparatus according to the first embodiment will be described.
First, the first control unit 30 to be described later converts document data as input data transmitted from a scanner unit (not shown) or the host unit 40 into pixel data.
The mechanism of the photosensitive drum 1 and the intermediate transfer belt 7 starts to be driven, and the charging unit 2 charges the surface of the photosensitive drum 1 uniformly.
Then, the exposure unit 3 irradiates light toward the surface of the photosensitive drum 1 based on the pixel data to form a latent image on the photosensitive drum 1, and the developing unit 4 develops the latent image into a toner image. To go. The toner image on the photosensitive drum 1 is primarily transferred from the contact portion with the intermediate transfer belt 7 to the intermediate transfer belt 7.
Before and after these, the registration roller 12 sends the recording material P conveyed from a paper supply means (not shown) toward the transfer means 8 at a predetermined timing, and the transfer means 8 is primarily transferred to the intermediate transfer belt 7. The toner image is secondarily transferred to the recording material P.
Then, the fixing unit 9 applies heat and pressure to the recording material P carrying the toner image to melt and solidify the toner image on the recording material P. The recording material on which the image has been formed is discharged outside the apparatus from a discharge unit (not shown).

Next, the 1st control means 30 concerning Embodiment 1 is explained in full detail.
In the first embodiment, a gradation pattern that is the same as or substantially the same as the average density of the gradation pattern in the case of a recording material with a flat surface is formed according to the density of the original image and the unevenness of the surface of the recording material. It is an example provided with the 1st control means 30 which produces | generates possible pixel data.

  As shown in FIG. 2, the first control means 30 includes a pattern type acquisition means 20 to which the pattern type detection sensor 10 is connected, a pattern data acquisition means 21, a decoding means 23, a pattern data storage means 24, The image processing means 25 and the exposure control means 27 to which the exposure means 3 is connected are serially connected in this order.

The pattern data acquisition unit 21 is connected to an encrypted pattern data storage unit 22, a large-capacity storage unit 28, and a network interface unit 26. The network interface unit 26 is connected to a host unit 40 that transmits a print job to the image forming apparatus via a network.
The image processing means 25 is connected to the image data storage means 11 for temporarily storing document data as input data.

The pattern type acquisition unit 20 is connected to the pattern type detection sensor 10 and detects the pattern type from the recording material P via the pattern type detection sensor 10.
The pattern type detected by the pattern type detection sensor 10 is an identifier for specifying or distinguishing the pattern of the concavo-convex portion existing on the recording material P (pattern type, at which position the concavo-convex portion exists). Or it comprises tag information, a sign, and other simple incidental information. The incidental information includes a serial number for managing the recording material P, information necessary for image formation, information for checking beforehand whether or not a correct format sheet is loaded for an output document, and the like. .

Examples of the pattern type recording means for recording the pattern type on the recording material P include a bar code, a QR code (registered trademark), a wireless IC chip embedded in the recording material P, and the like, and are not particularly limited. Further, character information in which the pattern type is directly or indirectly written may be printed.
Accordingly, the pattern type detection sensor 10 is a line sensor constituted by, for example, a CCD element in the case of a barcode or QR code, and an antenna that reads information in the chip in the case of a wireless IC chip. In the case of character information, it is a camera or a scanner.

Examples of the recording material P include a simple geometric figure having a height difference of about 150 μm at the maximum, and a periodic uneven portion on the entire surface such as resack paper as shown in FIG. . In the case of a recording material such as resack paper, when the base paper is cut to a specific size, the offset information of the uneven portion, that is, from which position on the paper the specific period C of the uneven portion pattern starts. Is different for each sheet, and information that can be recognized is recorded in the pattern type recording means.

Moreover, the recording material P in which an uneven part exists only in a specific region may be used. For example, as shown in FIG. 8, there is a format paper in which concave and convex portions 71 having a rectangular area are provided at two locations on the recording material P, and a pattern type recording means 70 is provided in the upper right portion in FIG. 8. The pattern type recording means 70 includes at least position information for recognizing at which position on the recording material P the uneven portion 71 exists. In this case, it is only necessary to check whether or not the correct format recording material P is loaded.
The concavo-convex portion 71 is, for example, a record column for a signature for authenticating the origin of the recording material P itself, which can be used instead of watermarking or hologram printing, a digital seal, a printing date, an issued serial number, and the like.

  Based on the pattern type obtained by the pattern type obtaining unit 20, the pattern data obtaining unit 21 is connected to the network via the mass storage unit 28 such as a hard disk built in the image forming apparatus or the network interface unit 26. The corresponding pattern data is searched and acquired from the mass storage means 41 held by the connected external host means 40. If the corresponding pattern data already exists in the pattern type recording means 24, the pattern data acquisition process can be omitted.

  As described above, the large-capacity storage unit 28 or the large-capacity storage unit 41 stores a plurality of pattern data in advance. It is preferable that the pattern data is encrypted for security. In the case of encrypted pattern data, it is acquired by the pattern data acquisition means 21 and stored in the encryption pattern data storage means 22.

The pattern data described above is information indicating the unevenness state of the surface of the recording material, such as the height distribution data of the unevenness portion of the recording material P, the resolution (sampling interval), and the like. It is associated with the acquired pattern type.
This pattern data is, for example, data obtained by measuring the height distribution of a 100 mm square area with sufficient accuracy, assuming that the resolution in the plane direction is 0.1 mm and the resolution in the height direction is 1/256 of the maximum height difference. In the case of processed data, the height level is 0 to 255 levels, that is, 1 byte precision, height data of about 1 Mbyte, and the resolution in the plane direction, maximum height difference or height per level. Composed.
When the concavo-convex portion exists only in a part of the recording material P, it is regarded as a certain height outside the recording material P.

The decrypting unit 23 decrypts the encrypted pattern data stored in the encrypted pattern data storage unit 22 and temporarily stores it in the pattern data storage unit 24. Decryption processing is not performed for unencrypted pattern data. In the case of unencrypted pattern data, it is preferable that the pattern data storage unit 24 deletes it immediately after the end of image formation.
The encrypted pattern data stored in the encrypted pattern data storage unit 22 may be continued for a certain period of time depending on security importance, printing frequency, and the like.

  In actual operation, since there are a plurality of pattern types depending on the type of recording material, a plurality of decryption keys for decrypting the encrypted pattern data are required. Therefore, a plurality of decryption keys are stored in the host means 40 (storage means) for transmitting the print job or other host means (storage means) connected on the network, and the host means 40 or other host means is stored in the host means 40. The decryption key is transmitted as a print authentication server that also serves as a pattern data database. At this time, the image forming apparatus transmits the serial number of the recording material P, the issued serial number, etc. to the host means for performing print authentication according to the management necessity.

  The pattern data storage unit 24 temporarily stores the pattern data as described above. In the case of encrypted pattern data, the decryption means 23 decrypts the encrypted pattern data, and the decrypted pattern data is temporarily stored.

In the case of a recording material having a concavo-convex portion, the image processing means 25 determines the density of the original image recognizable from the original data stored in the image data storage means 11 and the concavo-convex state of the recording material surface (the concavo-convex portion of the recording material P Height distribution data, pattern data indicating resolution (sampling interval), etc., pattern type (identification or distinction of uneven pattern on the recording material P (pattern type, where the uneven part is present) Etc.) to generate pixel data from identifiers or tag information, codes, other simple supplementary information, etc.).
That is, the image processing means 25 is used for a halftone pattern, a line pattern, or the like in the case of a flat recording material having no unevenness on the surface, with respect to the concavo-convex portion in the recording material or the entire image forming area of the recording material. Pixel data from which a gradation pattern is obtained that is the same or substantially the same as the average density of the gradation pattern is generated. In addition, normal pixel data without an uneven portion and portions other than the uneven portion generate original pixel data.

  A specific example of generation of pixel data of a recording material having an uneven portion will be described. It is assumed that pattern data has been acquired as a premise, and the halftone dot (one halftone dot) constituting the halftone dot pattern has 16 gradations of 4 × 4 pixel binary values as shown in FIG. A case where (# 1 to # 16) can be displayed will be described as an example.

  FIG. 4 shows a halftone dot pattern before correction (a halftone dot pattern in the case of a normal recording material having no irregularities) and a halftone dot pattern after correction (in the case of a recording material having irregularities at a certain height level). It is an example of a conversion function representing a correspondence relationship between halftone dot patterns. The conversion function generally varies with the height level as a parameter. In the case where halftone dots are generated for an area of a certain height level where the height on the recording material P is relatively low, if there is no image loss at halftone dots after the fourth gradation, the first The halftone dot patterns from the gradation (# 1) to the third gradation (# 3) are all the halftone dot patterns of the fourth gradation (# 4).

FIG. 5A is an example of halftone dot arrangement before correction, and shows a case where an image is formed by arranging halftone dot patterns of the first gradation (# 1).
In FIG. 5B, the image processing unit 25 replaces the halftone dot pattern of the first gradation (# 1) with the halftone dot pattern of the fourth gradation (# 4) before the correction in FIG. This shows a case where an image is formed so as to have the same average density as (the image density looks the same when viewed by a human).

  As described above, when outputting a halftone dot pattern that enables a low density image at a position of a relatively low area on the recording material P, each halftone dot has a higher image density after image formation. In addition to correcting the display number of pixels in such a direction, the distance between the halftone dots whose display is turned on is adjusted so as to be the same or substantially the same as the image density in a normal recording material having no uneven portion.

  The image processing means 25 considers the optical dot gain and the like, and optimizes the conversion function so that the halftone dot pattern is mixed and the gradation skip is not noticeable. The same processing can be applied to other gradation patterns such as a line pattern.

Further, the image level correction may be performed on the image data instead of performing the correction at the halftone dot generation stage.
FIG. 6 is a conversion function for image level correction at a certain height level in the case of a monochrome 256-tone image. An equivalent image can be obtained by generating pixel data for the corrected image data by, for example, an error diffusion method. On the other hand, in the case of a line image, pixel data may be generated so that the width of the line becomes wider in a region having a low height level.
The pixel data generated by the image processing unit 25 in this way is output to the exposure control unit 27.

  The exposure control unit 27 controls the exposure unit 3 using the pixel data generated by the image processing unit 25 so that a latent image can be formed on the surface of the charged photosensitive drum 1.

In the first control unit 30 according to the first embodiment configured as described above, first, the pattern type acquisition unit 20 acquires the pattern type from the sheet-like recording material P via the pattern type detection sensor 10. .
Next, the pattern data acquisition unit 21 searches and acquires the pattern data associated with the pattern type obtained by the pattern type acquisition unit 20 from the large capacity storage unit 28 or the large capacity storage unit 41.

The pattern data acquisition unit 21 stores the pattern data acquired by the pattern data acquisition unit 21 in the encrypted pattern data storage unit 22 when the pattern data is encrypted pattern data. If the pattern data is not encrypted, The data is temporarily stored in the pattern data storage unit 24.
When the encrypted pattern data is stored in the encrypted pattern data storage unit 22, the decryption unit 23 decrypts the encrypted pattern data and temporarily stores it in the pattern data storage unit 24.

The image processing means 25 is a network in the case of a normal recording material having no irregularities on the irregularities in the recording material or on the entire image forming area of the recording material based on the density, pattern data, and pattern type of the original image. Pixel data from which a gradation pattern is obtained that is the same or substantially the same as the average density of gradation patterns such as a dot pattern and a line pattern is generated, and the generated pixel data is output to the exposure control means 27. The image processing unit 25 also uses pattern type information to generate pixel data. However, when there is a concavo-convex portion in the entire image forming area of the recording material, the image processing unit 25 uses only the density of the original image and the pattern data. Pixel data may be generated.
The exposure control unit 27 uses the pixel data generated by the image processing unit 25 to control the exposure unit 3 so that a latent image can be formed on the surface of the charged photosensitive drum 1.

  As described above, the toner image on the photosensitive drum 1 is primarily transferred from the contact portion with the intermediate transfer belt 7 to the intermediate transfer belt 7. The conveyed recording material P is sent to the transfer means 8 at a predetermined timing, and the transfer means 8 secondarily transfers the toner image primarily transferred to the intermediate transfer belt 7 to the recording material P. Then, the fixing unit 9 applies heat and pressure to the recording material P carrying the toner image to melt and solidify the toner image on the recording material P. The recording material on which the image has been formed is discharged outside the apparatus from a discharge unit (not shown).

  As described above, according to the image forming apparatus according to the first embodiment, the same or substantially the same as that of a normal recording material having no concavo-convex portion with respect to the concavo-convex portion in the recording material or the entire image forming area of the recording material. Therefore, even in the case of a low adhesion amount image such as a highlight image or a line image in a concave portion of a recording material such as resack paper, a good image can be formed.

  Further, according to the image forming apparatus according to the first embodiment, when printing is performed using the recording material P having predetermined pattern data, a good image can be obtained. If not, it becomes clear that the image or character in the region where the unevenness is present is blurred or missing, and the image is improperly printed. If the recording material P to be used is not suitable, forgery can be prevented in advance by stopping image formation.

In the first embodiment, the pattern data is stored in an encrypted state, so that the security can be further improved in terms of security (for example, the same resack paper with respect to the original resack paper) Can be used to prevent the original from being copied).
Further, the encrypted pattern data is decrypted after obtaining the descrambling key by an external host means connected to the network, so that security security can be further strengthened.

(Embodiment 2)
The image forming apparatus according to the second embodiment is a modification of the first control unit 30 according to the first embodiment described above. That is, as shown in FIG. 10, this is an example in which the configuration of the first control unit described above includes the reflection pattern detection sensor 12 and the reflection pattern extraction unit 31. The components common to the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed description thereof is omitted.

  The image forming apparatus according to the second embodiment is connected to a reflection pattern detection sensor 12 including an optical line sensor configured by, for example, a CCD element, and the reflection pattern detection sensor 12 and to a pattern data acquisition unit 21. The reflection pattern extraction means 31 is provided.

The reflection pattern detection sensor 12 measures the reflectance distribution generated by the uneven state of the recording material P, and transmits data to the reflection pattern extraction unit 31.
The pattern type detection sensor 10 tries to detect the pattern type recorded on the recording material P, and when detecting the pattern type, transmits it to the pattern type acquisition means 20.

  The reflection pattern extraction unit 31 acquires the pattern period and offset information of the concavo-convex portion from the characteristics of the reflectance distribution of the recording material P detected by the reflection pattern detection sensor 12, and transmits the data to the pattern data acquisition unit 21. . When the pattern type exists in the recording material P, the process proceeds to the process in the pattern data acquisition unit 21.

  In addition, in the case of a recording material formatted with a concavo-convex structure, when only a pattern name or the like is recorded as a pattern type, or for some reason, the pattern type acquisition means 20 has acquired detailed information. When the position and range of the concavo-convex structure cannot be specified, the reflection pattern extraction unit 31 specifies the position and range where the concavo-convex part exists from the information detected by the reflection pattern detection sensor 12, and the pattern data acquisition unit 21 Send to.

According to the second embodiment, the effect of the first embodiment can be obtained even with the recording material P on which the pattern type information itself is not recorded. In addition, if the pattern type detection sensor 10 is a system which reads a barcode and QR code with an optical sensor, it can be used also as this reflection pattern detection sensor.
Further, the pattern type detection sensor 10 and the pattern type acquisition unit 20 may be replaced with the reflection pattern detection sensor 12 and the reflection pattern extraction unit 31.
Further, the pattern type recording means exemplified in the first embodiment is a bar code, and only the pattern name as the pattern type is recorded on the bar code, and the structure and position of the concavo-convex part is detected by the reflection pattern detection sensor 12. Information may be separated as detected.

(Embodiment 3)
In the image forming apparatus according to the third embodiment, the average density of the gradation pattern in the case of a recording material having a flat surface is the same or substantially the same, depending on the image density of the document and the unevenness of the surface of the recording material. In this way, the second control means for adjusting the exposure signal is provided. That is, the third embodiment includes a second control unit 30b including a power level conversion unit 50 that modulates the intensity of light emitted from the exposure unit 3 in accordance with the density, pattern data, and pattern type of the original image. In this example, the first control unit 30 according to the first embodiment described above is combined, and the components common to the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted. To do. The technical means for acquiring the pattern data of the recording material P is the same as that of the first embodiment, and the configuration part is configured to also serve as the first control means 30.

The image forming apparatus according to the third embodiment includes an exposure unit 3, a power level conversion unit 50, and an exposure control unit 27.
The exposure unit 3 includes a multi-tone writing light source that can be switched at least at two levels of exposure power (three levels when the exposure power is zero).

  As shown in FIG. 11, the power level conversion means 50 is connected so as to connect the pattern data storage means 24 and the exposure control means 27 across the image processing means 25, and the recording stored in the pattern data storage means 24. Based on the height distribution data of the concavo-convex portion of the material P, power modulation is performed so that the exposure power is increased at a deeper position of the concavo-convex portion, and is transmitted to the exposure control means 27.

  The exposure control means 27 is the same or substantially the same as the average density of the pixel data generated by the image processing means 25 (the halftone pattern, the line pattern, etc. in the case of a recording material having a flat surface with no irregularities. When the pixel data from which a gradation pattern such as is obtained is converted into a time series of exposure power, the exposure means 3 is controlled by power amplitude modulation.

Here is a specific example. The relative depth of the uneven portion of the recording material P is Dr, where the highest (shallow) location is the reference value Dr = 0, the power modulation coefficient α of the light source, the reference exposure power amplitude, that is, the exposure power when using a normal recording material When the amplitude is P0 and the amount of increase in exposure power amplitude per level is ΔP, the exposure power amplitude P per dot is obtained based on the following (Equation 1).
P = P0 + ΔPα (Dr) (Formula 1)
ΔP is a parameter that is adjusted so that a good image can be obtained, and depends on the maximum height difference of the uneven portion of the recording material P.

FIG. 12 shows an example in which the exposure power is 4 levels in the functional relationship α = α (Dr) between the power modulation coefficient α and the relative depth Dr.
The means for amplitude-modulating the exposure power can be realized by an existing control technique when using a laser diode light source or an LED light source, for example, current control or duty ratio control.

  In general, if the exposure power is large, the toner adhesion amount on the photosensitive drum 1 after development or the toner stack thickness increases. The dot size in the halftone is large, and in the case of a line image, the line becomes thick. The relationship (1) between the exposure power and the toner adhesion amount on the image carrier can be quantified experimentally. It is also possible to experimentally find the relationship (2) between the height of the concavo-convex portion of the recording material P and the toner adhesion amount so that a good image can be obtained.

Therefore, from the relationship (1) and the relationship (2), it is possible to find the functional relationship of the light intensity of the light source to be controlled with respect to the height of the uneven portion of the recording material P as shown in FIG.
With respect to the height distribution data included in the pattern data of the recording material P, the power level of the writing light is modulated for each dot using the function of Expression 1 with an appropriate resolution.

  The power level modulation of the writing light for each dot uses original pixel data (pixel data when there is no uneven portion), modulates only the exposure power level, or image processing means as in the first embodiment. It is also possible to generate pixel data (pixel data of the concavo-convex portion) at 25 and perform amplitude modulation of the power level of the writing light using the pixel data.

  According to the third embodiment, as the height difference of the concavo-convex portion is larger, the amount of toner adhering to the photosensitive drum 1 is increased by increasing the exposure power. Therefore, transfer that occurs during transfer to the recording material is performed. It is possible to reduce blurring and loss of images due to dust.

(Embodiment 4)
In the image forming apparatus according to the fourth embodiment, the average density of the gradation pattern in the case of a recording material having a flat surface is the same or substantially the same, depending on the image density of the document and the unevenness of the surface of the recording material. In this way, the third control means for adjusting the developing bias is provided. That is, the fourth embodiment includes a development bias control means 60 for adjusting the development bias applied to the development means in accordance with the density, pattern data, and pattern type of the document image, and a development process control means 29. The control unit 30c and the first control unit 30 according to the first embodiment described above are combined, and the components common to the first embodiment are denoted by the same reference numerals as those in the first embodiment. Detailed description will be omitted. The technical means for acquiring the pattern data of the recording material P is the same as that of the first embodiment, and the configuration part is configured to also serve as the first control means 30.

As shown in FIG. 13, the image forming apparatus according to the fourth embodiment includes a development bias control unit 60 and a development process control unit 29.
The development bias control means 60 is connected to the pattern data storage means 24, extracts the height difference feature quantity H from the height distribution data stored in the pattern data storage means 24, and is based on the height difference feature quantity H. The developing bias Vb is calculated and output to the developing process control means 29 described later.
The development process control unit 29 is connected to the development bias control unit 60 and controls the development bias of the development unit 4 using the development bias Vb.

Here is a specific example. β is a development bias coefficient having a height difference feature amount H as a function, Vb0 is a reference development bias, that is, a development bias when using normal paper, and ΔVb is an adjustment parameter depending on a specific configuration of the image forming apparatus. At this time, the developing bias Vb is calculated based on the following (formula 2).
Vb = Vb0 + β (H) ΔVb (Formula 2)
The height difference feature amount H is defined by, for example, H = σ / σmax, where σ is the standard deviation (same as the RMS roughness) in the height distribution of the recording material, and σmax is the maximum standard deviation to be assumed. The parameters are different for each material.
In addition to the standard deviation, a maximum height difference may be used.
ΔVb also depends on a specific evaluation method of the height difference feature amount H.

  FIG. 14 illustrates the relationship between the height difference feature amount H and the development bias coefficient β. FIG. 14 shows a case where the relationship between the height difference feature amount H and the development bias coefficient β changes linearly and β = 1 is restricted when H> 1, but the height difference feature amount of the recording material P is shown. The characteristic is that the larger the H is, the higher the developing bias Vb is adjusted.

The relationship (3) between the developing bias Vb and the toner adhesion amount (M / A) can be quantified experimentally. Further, the relationship (4) between the height difference feature amount and the adhesion amount (M / A) can also be quantified experimentally.
Therefore, from the relationship (3) and the relationship (4), the functional relationship of the development bias Vb to be controlled with respect to the height difference feature amount H as shown in FIG.

  The adjustment of the developing bias Vb is performed by using original pixel data (pixel data when there is no uneven portion), adjusting only the developing bias Vb, or by the image processing means 25 using the image processing unit 25 as in the first embodiment. Alternatively, the pixel data of the uneven portion may be generated, and the development bias Vb may be adjusted using the pixel data.

  According to the fourth embodiment, the larger the height difference of the concavo-convex portion, the larger the amount of toner adhering to the photosensitive drum 1 by increasing the developing bias. Therefore, the transfer that occurs when transferring to the recording material It is possible to reduce blurring and loss of images due to dust.

(Embodiment 5)
As shown in FIG. 15, the image forming apparatus according to the fifth embodiment is an example in which a first control unit 30, a second control unit 30b, and a third control unit 30c are combined. Since the above configuration has been described above, a detailed description thereof will be omitted. The technical means for acquiring the pattern data of the recording material P is the same as that of the first embodiment, and the configuration part is configured to also serve as the first control means 30.
According to the fifth embodiment, more detailed control can be performed.

The image forming apparatus according to the present embodiment has been described above. However, the above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto. Various modifications can be made without departing from the scope of the invention.
For example, the image forming apparatus according to the present embodiment is applied to a monochrome image forming apparatus, but can be applied to a tandem color image forming apparatus.
The present invention is also applicable to ticketing / printing systems such as certificate stamps with enhanced forgery prevention measures.

1 Photosensitive drum (photoconductor)
3 Exposure means 4 Development means 10 Pattern type detection sensor 11 Image data storage means 20 Pattern type acquisition means 21 Pattern data acquisition means 22 Encrypted pattern data storage means 23 Decryption means 24 Pattern data storage means 25 Image processing means 26 Network interface means 27 Exposure control means 28 Mass storage means 30 First control means 30b Second control means 30c Third control means 40 Host means 50 Power level conversion means 60 Development bias control means

JP 2006-267486 A JP 2006-018096 A

Claims (9)

Generates pixel data that can form a gradation pattern that is the same or substantially the same as the average density of the gradation pattern in the case of a recording material with a flat surface, depending on the density of the original image and the surface roughness of the recording material. First control means to:
An image forming apparatus comprising: an exposure unit configured to irradiate a photoconductor with light based on the pixel data generated by the first control unit to form a latent image on the photoconductor. A second exposure signal is adjusted so as to be equal to or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the image density of the document and the surface roughness of the recording material. Control means;
An image forming apparatus comprising: an exposure unit configured to irradiate a photoconductor with light based on an exposure signal adjusted by the second control unit to form a latent image on the photoconductor. A third bias for adjusting the developing bias so as to be the same as or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the image density of the original and the surface roughness of the recording material. Control means;
An image forming apparatus comprising: a developing unit that develops the latent image formed on the photosensitive member into a toner image by applying a developing bias adjusted by the third control unit. Generates pixel data that can form a gradation pattern that is the same or substantially the same as the average density of the gradation pattern in the case of a recording material with a flat surface, depending on the density of the original image and the surface roughness of the recording material. First control means to:
A second exposure signal is adjusted so as to be equal to or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the image density of the document and the surface roughness of the recording material. Control means;
An exposure unit that irradiates a photoconductor with light based on the pixel data generated by the first control unit and an exposure signal adjusted by the second control unit to form a latent image on the photoconductor. An image forming apparatus comprising: Generates pixel data that can form a gradation pattern that is the same or substantially the same as the average density of the gradation pattern in the case of a recording material with a flat surface, depending on the density of the original image and the surface roughness of the recording material. First control means to:
Exposure means for irradiating the photoconductor with light based on the pixel data generated by the first control means to form a latent image on the photoconductor;
A third bias for adjusting the developing bias so as to be the same as or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the image density of the original and the surface roughness of the recording material. Control means;
An image forming apparatus comprising: a developing unit that develops the latent image formed on the photosensitive member into a toner image by applying a developing bias adjusted by the third control unit. Generates pixel data that can form a gradation pattern that is the same or substantially the same as the average density of the gradation pattern in the case of a recording material with a flat surface, depending on the density of the original image and the surface roughness of the recording material. First control means to:
A second exposure signal is adjusted so as to be equal to or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the image density of the document and the surface roughness of the recording material. Control means;
A third bias for adjusting the developing bias so as to be the same as or substantially the same as the average density of the gradation pattern in the case of a recording material having a flat surface, depending on the image density of the original and the surface roughness of the recording material. Control means;
An exposure unit that irradiates a photoconductor with light based on the pixel data generated by the first control unit and an exposure signal adjusted by the second control unit to form a latent image on the photoconductor. When,
An image forming apparatus comprising: a developing unit that applies a developing bias adjusted by the third control unit to develop a latent image formed on the photoconductor into a toner image. The first control means includes
Either one of a pattern type acquisition unit that acquires a pattern type from the recording material, or a reflection pattern extraction unit that extracts a reflection pattern of the recording material and acquires information on an uneven state on the surface of the recording material, or , Both sides,
Pattern data storage means in which pattern data indicating the uneven state of the surface of the recording material is stored;
The pattern data acquisition means for acquiring information on the uneven state of the surface of the recording material from the pattern data storage means based on the pattern type acquired by the pattern type acquisition means. The image forming apparatus according to any one of 1, 4, 5, and 6. The pattern data is encrypted, and encrypted pattern data storage means in which the encrypted pattern data is stored;
8. The apparatus according to claim 7, further comprising: a decryption unit that obtains the encrypted pattern data from the encrypted pattern data storage unit and that obtains the encrypted pattern data and decrypts the obtained encrypted pattern data. The image forming apparatus described. Comprising storage means for storing a decryption key for decrypting the encrypted pattern data;
The pattern data acquisition means acquires the decryption key from the storage means,
The image forming apparatus according to claim 8, wherein the decryption unit decrypts the encrypted pattern data using the acquired decryption key.

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