JP2010094991A - Stencil plate-making apparatus and stencil printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stencil plate-making apparatus which makes a stencil optimum in response to a manuscript and in the entire manuscript. <P>SOLUTION: The stencil plate-making apparatus includes: an image region determining unit 4 which determines an image region attribution to be sorted to a plurality of ranks from a binary image to a gradation image, in the image region of each pixel or predetermined block of an inputted image data; a perforating means for forming a perforated image on stencil base paper based on the image data by selectively heating each heating element of a thermal head 21 in which a plurality of heating elements are arranged in row in a main scanning direction; and a perforated printing plate making control unit 8 for variably controlling the perforating area in the stencil base paper to be perforated by the perforation means according to the image region attributions determined by the image region determining unit 4. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a stencil making apparatus and a stencil printing apparatus, and in particular, performs local perforation control according to the image area attribute for each image area of image data, thereby producing an optimum stencil according to the original and over the entire original. The present invention relates to a stencil plate making apparatus that can be created, and a stencil printing apparatus that can realize a high-quality printed image faithful to an original.

  In the stencil printing apparatus, an image read from an original is converted into black and white image information (hereinafter referred to as black and white data), and the stencil sheet is selectively heated and punched by a heating element based on the black and white data. A perforated image is formed on the stencil sheet based on the image data. In the formation of the perforated image, among the black and white pixels included in the black and white data, the white pixels are not heated and perforated, but the black pixels are heated and perforated to form holes through which ink passes (the white pixels Some of them may be heated to the extent that they are not perforated).

  In the plate making process, the user selects a document mode (character mode, photo mode, character / photo mode, etc.) according to the type of document. Here, the character mode is a binary image original such as a character or a line drawing, the photo mode is a gradation image original such as a photo or halftone dot, and the character / photo mode is a character and a photo. Each is selected in the case of mixed originals. When the document mode is selected, predetermined image processing is performed on the monochrome data in accordance with each mode.

  By the way, since there are many isolated parts in the gradation of the highlight part in a photographic document, the heat storage in the heating element is small, and the heat from the heating element is difficult to be transferred during heat drilling. However, it is often found that no perforation (hereinafter referred to as non-occurrence) occurs. When such a non-occurrence occurs, the pixel in that portion becomes an image defect such as a blur (white spot). In addition, even if the holes are perforated, the perforated area may be smaller than that calculated, resulting in variations in the perforated area (perforated variation). Increasing the black pixel perforation area to prevent these problems is effective for isolated areas in the photo mode. Since the perforated area of the pixel is larger than usual, the fine line is likely to be broken. The ruled line breakage is a state in which adjacent perforations in the stencil sheet are cut and the holes are connected to each other, which causes image defects.

  In order to deal with such a problem of image defects, for example, in Japanese Patent Application Laid-Open No. 2006-341556 “Stencil making apparatus and stencil printing apparatus”, scattered black pixel patterns in which black pixels are not adjacent in the main scanning direction and the sub-scanning direction ( In the case of an isolated portion), a method has been proposed in which heating by a heating element is controlled so that a perforated area per pixel is larger than that in a continuous black pixel pattern (thin line).

  Japanese Patent Laid-Open No. 2004-155170, “Printing Device”, in order to obtain a high-quality print image faithful to a document, according to the user's document mode (character mode, photo mode, or character / photo mode) selection, There has been proposed a method of variably controlling the printing pressure by the pressing means when forming a printed image. Specifically, the printing pressure is controlled to be lower when the photo mode is selected than when the text / photo mode is selected, and when the text / photo mode is selected than when the text mode is selected. At the same time, when the photo mode is selected, the perforation area density is coarser than when the text / photo mode is selected, and when the text mode is selected, the perforation area density is higher than when the text / photo mode is selected. A method for setting energy parameters has also been proposed.

JP 2006-341556 A JP 2004-155170 A

  Generally, photographic originals have a lower printing rate than text originals, so when looking at each heating element, there is a tendency for heat storage when it generates heat and the influence of heat from surrounding pixels (heat transfer) to be less. is there. On the other hand, in the technique disclosed in Patent Document 1, although the perforated area is increased for the isolated portion of the photographic original, the thin line of the same photographic original remains the same perforated area as usual. There is a high possibility that misfire or perforation variation will occur.

  Further, in the technique (disclosed in Patent Document 2) in which the punching surface density is variably controlled in accordance with the user's original mode (character mode, photo mode, or character / photo mode) selection, the perforation surface density is relative when the character mode is selected. Is controlled tightly (increase the perforation area), so that the filling of the solid is improved, but the influence of heat generation (heat transfer) increases, so the top / end difference with respect to the sub-scanning direction in the solid portion There is a problem that becomes larger. Further, when the photographic mode is selected, the perforation surface density is controlled to be relatively coarse (the perforation area is small), so that the graininess in the halftone region is suppressed, but there is a high possibility that it will not occur at an isolated point.

  As described above, when the perforation area is increased, non-occurrence at an isolated point can be prevented, but the top / end difference with respect to the sub-scanning direction in the solid portion is increased, and graininess is generated in the halftone area. On the other hand, when the perforated area is reduced, the graininess in the halftone region is suppressed, but it does not occur at the isolated point. Especially when the text / photo mode is selected, the perforated surface density is controlled uniformly with a relatively middle level, so the uniformity of the solid in the text (binary image) area cannot be maintained, and it is isolated in the photo (tone image) area. There has been a problem in that the occurrence of defects in dots cannot be prevented and graininess is generated in the halftone area, and as a result, a high-quality printed image faithful to the original cannot be obtained.

  The present invention has been made in view of the above-described conventional circumstances, and performs local punching control according to an image area attribute for each image area (pixel or predetermined block) of image data, and according to a document. It is another object of the present invention to provide a stencil making apparatus capable of producing an optimum stencil over the entire document.

  Another object of the present invention is to provide a stencil printing apparatus capable of realizing a high-quality printed image faithful to an original.

  In order to solve the above-described object, the invention according to claim 1 is an image that is classified in multiple stages between a binary image and a gradation image with respect to a pixel of input image data or an image area for each predetermined block. An image area determining means for determining an area attribute; a punching means for forming a punched image on a stencil sheet based on the image data; and the punching means by the punching means according to the image area attribute determined by the image area determining means. And a perforation control means for variably controlling a perforation area perforated on the base paper.

  According to a second aspect of the present invention, in the stencil plate making apparatus according to the first aspect, the perforating means includes a thermal head in which a plurality of heating elements are arranged in the main scanning direction. The heating element is selectively heated to form a perforated image on the stencil sheet based on the image data, and the perforation control means variably controls the perforation area by adjusting the energy applied to the thermal head. It is characterized by.

  According to a third aspect of the present invention, in the stencil plate making apparatus according to the second aspect, the punching control means variably controls the punching area by adjusting the power supplied to the thermal head or the energizing time of the power. It is characterized by that.

  According to a fourth aspect of the present invention, in the stencil plate making apparatus according to any one of the first to third aspects, the image area determination means is a binary image of an image in the image area for each image area. A feature indicating the uniqueness is extracted, and based on the feature, it is determined whether the image area attribute is a binary image, a gradation image, or an intermediate image of the binary image and the gradation image. To do.

  According to a fifth aspect of the present invention, in the stencil making apparatus according to the fourth aspect, when the image area attribute is a gradation image, the perforation control means is a relatively larger perforation area than in the case of a binary image. As described above, when the image area attribute is an intermediate image, control is performed so that the perforated area is relatively smaller than that of a binary image.

  According to a sixth aspect of the present invention, in the stencil plate making apparatus according to any one of the fourth or fifth aspect, the image area determining means has an image area attribute between the binary image and the gradation image. Image areas that are determined to be images are classified in multiple stages between an image that is closer to a binary image and an image that is closer to a gradation image in accordance with the feature amount indicating the likelihood of a binary image. It is characterized by determining an attribute.

  According to a seventh aspect of the present invention, in the stencil plate making apparatus according to any one of the fourth to sixth aspects, printing according to a character mode or a photographic image for performing a printing operation according to a character image or the like. A mode setting means for setting a photographic mode for performing an operation, and a character / photo mode for performing a printing operation in accordance with a mixed image such as a character image and a photographic image, wherein the punching control means has a binary image area attribute A control amount (hereinafter referred to as a reference control amount) given to the punching means at the time of an image is variable according to the setting of the mode setting means.

  According to an eighth aspect of the present invention, in the stencil plate making apparatus according to the seventh aspect, the punching control means has a larger punching area when the character mode is set by the mode setting means than when the character / photo mode is set. A reference control amount is set, and when the photo mode is set, a reference control amount that sets a smaller punching area than when the character / photo mode is set is set.

  The invention according to claim 9 includes the stencil plate making apparatus according to any one of claims 1 to 8.

  Further, the invention according to claim 10 is the stencil printing apparatus according to claim 9, further comprising a document reading means, wherein the image area determination means performs image area attribute determination on the image data input from the document reading means. It is characterized by performing.

  According to the first aspect of the present invention, the perforation area perforated on the stencil sheet by the perforation means is variable by the perforation control means according to the pixel determined by the image area determination means or the image area attribute for each predetermined block. Therefore, it is possible to perform local punching control according to the image area attribute for each image area (pixel or predetermined block) of the image data, and as a result, an optimum stencil according to the original and over the entire original is obtained. A stencil plate making apparatus that can be produced can be provided.

  According to a second aspect of the present invention, a thermal head in which a plurality of heating elements are arranged in the main scanning direction is used as the punching means, and the energy applied to the thermal head is adjusted by the punching control means. The area is variably controlled, and in particular, according to the invention described in claim 3, the perforation area is variably controlled by adjusting the power supplied to the thermal head by the perforation control means or the energization time of the power. Application to the plate making process is possible, and the perforation area can be variably controlled with a relatively simple control circuit configuration that adjusts the power or the energization time of the power.

  In the invention according to claim 4, the image area determining means extracts a feature indicating the binary image likeness of the image in the image area for each image area, and based on the feature, the image area attribute is a binary image, gradation It is determined whether the image is an intermediate image of a binary image or a gradation image. Here, as the feature information indicating the binary image-likeness of the image, for example, high-density pixel-likeness, fine-line pixel-likeness, edge sharpness degree, or edge so as to be able to discriminate binary images of various modes The image area attribute is determined by the LUT method, the fuzzy inference method, or the like based on the feature information using the pixel quality.

  For example, when using the degree of edge sharpness and edge pixel likeness as characteristic information indicating the binary image likeness of an image, and separating the edge pixel likeness by the distance from the detected edge, the pixels in the image area When the image area attribute is within the first predetermined distance from the edge, the image area attribute is determined to be a binary image, and when the pixels in the image area are outside the second predetermined distance (longer than the first predetermined distance) from the edge The image area attribute is determined to be a gradation image, and if the pixels of the image area are outside the first predetermined distance and within the second predetermined distance from the edge, the image area attribute is an intermediate image. It will be judged. Thereby, it is possible to accurately determine the image area attribute without erroneous determination.

  In the invention according to claim 5, when the image area attribute is a gradation image, the perforation control means makes the perforation area relatively larger than that of the binary image, and the image area attribute is an intermediate image. In this case, control is performed so that the perforated area is relatively smaller than that of the binary image. That is, since the image area attribute is determined to be a gradation image such as a photograph or a halftone dot, the image area is perforated with a relatively large perforation area (DL), so that the occurrence of an isolated point can be prevented. In the image area where the image area attribute is determined to be an intermediate image of the binary image and the gradation image, the image area is perforated with a relatively small perforation area (DS). In the image area in which the image area attribute is determined to be a binary image such as a character or a line drawing, the image is perforated with a perforation area (DM) intermediate between the gradation image and the intermediate image. The top / end difference with respect to the sub-scanning direction in the solid portion can be suppressed. In this manner, local punching control can be performed according to the image area attribute for each image area of the image data, and as a result, an optimum stencil can be created according to the original and over the entire original.

  In the invention according to claim 6, the image area attribute is determined by the image area determining means according to the feature amount indicating the binary image characteristic for the image area whose image area attribute is determined to be an intermediate image between the binary image and the gradation image. Thus, image area attributes classified in multiple stages between an image closer to a binary image and an image closer to a gradation image are determined. Similar to the above-described example, when the degree of edge sharpness and edge pixel likeness are used as feature information indicating the binary image likeness of the image, and the edge pixel likeness is classified by the distance from the detected edge, For the image area whose area attribute is determined to be an intermediate image, the image area attribute is classified into multiple stages according to the distance from the edge. As a result, it is possible to finely perform local punching control according to the image area attribute for each image area of the image data, and as a result, it is possible to create a more optimal stencil according to the original and over the entire original. .

  For example, when the image area pixel is within a third predetermined distance from the edge (longer than the first predetermined distance), the image area attribute is determined to be an intermediate image from the binary image, and the image area pixel is When it is outside the fourth predetermined distance (longer than the third predetermined distance and shorter than the second predetermined distance) from the edge, the image area attribute is determined to be an intermediate image from the gradation image, and the pixels in the image area are further edged From the third predetermined distance and within the fourth predetermined distance, the image area attribute is determined to be the second intermediate image. In the image area in which the image area attribute is determined to be the second intermediate image, the relatively small perforated area (DS), and in the image area in which the image area attribute is determined to be the intermediate image from the binary image, A perforation area (DS1) between the perforation area (DM) when the image area attribute is a binary image and the perforation area (DS) when the image area attribute is a second intermediate image, and the image area attribute is a gradation image In the image area determined to be an intermediate image, a perforation area (DS2) between the perforation area (DL) when the image area attribute is a gradation image and the perforation area (DS) when the second intermediate image is used And drill each. As a result, the difference between the perforated areas is gradually filled at the boundary between the image area of the binary image and the image area of the intermediate image and the boundary between the image area of the intermediate image and the image area of the gradation image. And local drilling control can be performed more finely.

  According to the seventh aspect of the present invention, the reference control amount given to the punching means when the image area attribute is a binary image can be varied according to the setting of the character mode, photo mode or character / photo mode by the mode setting means. In particular, in the invention described in claim 8, a reference control amount that provides a larger punching area than that in the character / photo mode setting is set when the character mode is set, and a smaller punching area than that in the character / photo mode setting when the photo mode is set. Set the reference control amount.

  The reference control amount is variable according to the setting of the document mode (character mode, photo mode or character / photo mode), the reference control amount suitable for each document is set, and the image area for each image data image area By performing local punch control according to the attribute, the punch control amount is set in two stages, and finer punch control can be performed. As a result, depending on the document and over the entire document A more optimal stencil can be created.

  In the invention described in claim 9, the stencil plate making apparatus described in any one of claims 1 to 6 is provided, and in particular, in the invention described in claim 10, the image area determining means is a document reading device. Image area attribute determination is performed on the image data input from the means. Thereby, local punch control can be performed according to the image area attribute for each image area (pixel or predetermined block) of the image data, and an optimum stencil is created according to the original and over the entire original. As a result, it is possible to provide a stencil printing apparatus that can realize a high-quality printed image faithful to the original.

It is a block diagram explaining the basic composition of the part which performs a plate-making process in the stencil printing apparatus which concerns on the Example of this invention. It is a block diagram explaining the internal structure of the stencil printing apparatus of an Example. It is a block diagram explaining the functional block of the stencil printing apparatus of an Example. FIG. 3 is a configuration diagram of an image area determination unit 4 and its surroundings according to the first exemplary embodiment. It is explanatory drawing explaining the image area attribute determined by the image area determination part 4 of Example 1 according to various signals. 3 is a circuit diagram illustrating a configuration of a thermal head 21. FIG. 4 is a timing chart illustrating various signals for the thermal head 21. It is explanatory drawing explaining 3 types of determination results (a character, a photograph, and the middle). 6 is a configuration diagram of an image area determination unit 4 of Embodiment 2. FIG. It is explanatory drawing explaining the image area attribute determined by the image area determination part 4 of Example 2 according to various signals.

  Examples of the stencil plate making apparatus and stencil printing apparatus of the present invention will be described below. Since the stencil printing apparatus is included in the stencil printing apparatus, in the following description, the stencil printing apparatus will be exemplified as an apparatus to which the present invention is applied, and the stencil printing apparatus of the present invention will also be described.

  First, with reference to FIG. 1, a basic configuration and an outline of a part for performing plate making processing or a stencil plate making apparatus in a stencil printing apparatus according to an embodiment of the present invention will be described. As shown in the figure, as basic components of the stencil printing apparatus, a document reading unit 2, an image processing unit 3 including an image area determination unit 4, a density conversion unit 5 and a halftone processing unit 6, and a stencil plate making A control unit 8 and a thermal head 21 are provided.

  In the image processing unit 3, the image area determination unit (corresponding to the image area determination unit in the claims) 4 performs two processing on pixels of image data read by the document reading unit 2 or image areas for each predetermined block. Image area attributes classified in multiple stages between a value image and a gradation image are determined. Specifically, for each image area, a feature indicating the binary image likeness of the image in the image area is extracted, and based on the feature, the image area attribute is a binary image, a gradation image, and a binary image and a gradation image. The intermediate image is determined.

  Here, as the feature information indicating the binary image-likeness of the image, for example, high-density pixel-likeness, fine-line pixel-likeness, edge sharpness degree, or edge so as to be able to discriminate binary images of various modes The image area attribute is determined by the LUT method, the fuzzy inference method, or the like based on the feature information using the pixel quality. For example, when using the degree of edge sharpness and edge pixel likeness as characteristic information indicating the binary image likeness of an image, and separating the edge pixel likeness by the distance from the detected edge, the pixels in the image area When the image area attribute is within the first predetermined distance from the edge, the image area attribute is determined to be a binary image, and when the pixels in the image area are outside the second predetermined distance (longer than the first predetermined distance) from the edge The image area attribute is determined to be a gradation image, and if the pixels of the image area are outside the first predetermined distance and within the second predetermined distance from the edge, the image area attribute is an intermediate image. It will be judged.

  In addition, with respect to an image area whose image area attribute is determined to be an intermediate image between a binary image and a gradation image, the image area attribute is further reduced from an image closer to the binary image according to the feature amount indicating the characteristic of the binary image. You may make it determine the image area attribute classified into a multistep between the images close | similar to a tone image. For example, when the image area pixel is within a third predetermined distance from the edge (longer than the first predetermined distance), the image area attribute is determined to be an intermediate image from the binary image, and the image area pixel is When it is outside the fourth predetermined distance (longer than the third predetermined distance and shorter than the second predetermined distance) from the edge, the image area attribute is determined to be an intermediate image from the gradation image, and the pixels in the image area are further edged From the third predetermined distance and within the fourth predetermined distance, the image area attribute is determined to be the second intermediate image.

  Note that, for the image area for each pixel of the image data, a method for determining image area attributes classified in multiple stages from a binary image to a gradation image is described in “Image processing apparatus and disclosed in Japanese Patent No. 3755854”. A method for determining image area attributes classified into a binary image, a gradation image, and an intermediate image with respect to an image area for each predetermined block of image data has been proposed in the “two-dimensional line feature amount calculation device”. And "Image attribute determination method and apparatus" disclosed in Japanese Patent No. 3392798. You may apply these methods to the image area determination part 5 of a present Example. The word “block” used in the present specification has the meaning disclosed in Japanese Patent No. 3392798, and the method disclosed in the same gazette is also used as it is for dividing the block.

  Next, the density conversion unit 5 performs density conversion by selecting a density conversion curve corresponding to the image area attribute determined by the image area determination unit 4. For example, in the “image processing apparatus” disclosed in Japanese Patent Application Laid-Open No. 8-51538, area determination (determination of image area attribute in this specification) is performed for each pixel of image data in which a binary image and a gradation image are mixed. A method for performing density conversion by selecting a density conversion curve corresponding to the image area attribute is proposed, and the prior art is applied to the processing of the image area determination unit 4 and the density conversion unit 5 of the present embodiment. Also good.

  Further, the halftone processing unit 6 performs halftone processing on the image data after density conversion. That is, for the image data of the image area of which the image area attribute is a binary image, simple binarization processing is performed in which black and white are determined based on the threshold value, and the image area attribute is an image area of a gradation image or an intermediate image. For the image data, halftone dot / error diffusion processing is performed so that the density is expressed by the density of surrounding pixels. For this halftone process, a known technique may be applied as it is.

  Next, the stencil plate making control unit (corresponding to the perforation control means in the claims) 8 receives the image data after image processing and the image area attribute information for each image area from the image processing unit 3, and receives the image area attribute. Accordingly, the perforation area perforated on the stencil sheet is variably controlled by the perforation means. Specifically, the punching means includes a thermal head 21 in which a plurality of heating elements are arranged in the main scanning direction, and each heating element of the thermal head 21 is selectively heated to form image data. Based on this, a perforated image is formed on the stencil sheet, and the stencil plate making control unit 8 adjusts the energy applied to the thermal head 21 to variably control the perforated area. That is, the perforation area is variably controlled by adjusting the power supplied to the thermal head 21 or the energization time of the power.

  More specifically, the stencil plate making control unit 8 makes the perforation area relatively larger than that of the binary image when the image area attribute is a gradation image, and when the image area attribute is an intermediate image. Control is performed so that the perforated area is relatively smaller than that of the binary image. That is, the image area attribute is determined to be a gradation image such as a photograph or a halftone dot, and the image area attribute is intermediate between the binary image and the gradation image. In the image area determined to be an image, the image is perforated with a relatively small perforation area (DS), and in the image area where the image area attribute is determined to be a binary image such as a character or a line image, the gradation image and the intermediate image Drill with a medium drilling area (DM).

  Further, the classification of image area attributes is not limited to the three levels of the binary image, the gradation image, and the intermediate image of the binary image and the gradation image, and may be in multiple stages.

  For example, an image area whose image area attribute is determined to be an intermediate image between a binary image and a gradation image by the image area determination unit 4 is changed to a binary image according to a feature amount indicating the characteristic of a binary image. Image area attributes that are classified in multiple stages between an image close to a gradation image from a close image are determined. Here, when the degree of edge sharpness and edge pixel likeness are used as feature information indicating the binary image likeness of an image, and the edge pixel likeness is classified by the distance from the detected edge, the image area attribute is an intermediate image. The image area attributes are classified into multiple stages according to the distance from the edge.

  For example, when the image area pixel is within a third predetermined distance from the edge (longer than the first predetermined distance), the image area attribute is determined to be an intermediate image from the binary image, and the image area pixel is When it is outside the fourth predetermined distance (longer than the third predetermined distance and shorter than the second predetermined distance) from the edge, the image area attribute is determined to be an intermediate image from the gradation image, and the pixels in the image area are further edged From the third predetermined distance and within the fourth predetermined distance, the image area attribute is determined to be the second intermediate image.

  In this case, the stencil plate making control unit 8 has a relatively small perforated area (DS) in the image area in which the image area attribute is determined to be the second intermediate image, and has an image area attribute in the middle of the binary image. In the image area determined to be an image, the perforation area (DS1) is intermediate between the perforation area (DM) when the image area attribute is a binary image and the perforation area (DS) in the case of the second intermediate image. In the image area in which the image area attribute is determined to be an intermediate image from the gradation image, the perforation area (DL) when the image area attribute is the gradation image and the perforation area (DS) when the image area attribute is the second intermediate image Are respectively drilled in the middle drilling area (DS2).

  Next, with reference to FIG. 2 and FIG. 3, the internal structure of the stencil printing apparatus according to the embodiment of the present invention and the functional configuration relating to the control system will be described. Here, FIG. 2 shows the stencil printing of this embodiment. FIG. 3 is a block diagram illustrating the internal structure of the apparatus, and FIG. 3 is a block diagram illustrating functional blocks of the stencil printing apparatus according to the present embodiment.

  First, the overall configuration of the stencil printing apparatus 1 will be described. As shown in FIG. 2, the stencil printing apparatus 1 of this embodiment is roughly composed of a document reading unit 10, a plate making / writing unit 20, a cutter unit 30, and a printing unit 40.

  The document reading unit 10 is a mechanism for performing a document reading process. The document reading unit 10 sets a document 7 that is a copy object, and a document sensor that detects the document 7 set on the document setting table 12. 17, a document conveying roller pair 14 that is rotationally driven by a detection signal of the document sensor 17, a contact image sensor 11 that optically reads an image of the conveyed document 7 and converts it into an analog electric signal, and an image A document discharge roller pair 15 for discharging the document 7 read by the sensor 11 to the document discharge tray 19 is provided.

  The document IN sensor 16 is a means for detecting the conveyed document 7 and determines the start of the plate making / writing unit 20 described later. Further, the document transport roller pair 14 and the document discharge roller pair 15 are rotationally driven by a stepping motor 18 as indicated by dotted lines in the figure.

  In the document reading unit 10, when a control signal (not shown) receives a detection signal from the document sensor 17, the document transport roller pair 14 is rotationally driven to transport the document 7 in a predetermined direction. 7 is optically read. The original 7 from which the image has been read is discharged to the original discharge tray 19 by the original discharge roller pair 15. The analog electrical signal for one plate read by the image sensor 11 is converted to digital data by an A / D converter (not shown) and then sent to the image processor 4 (not shown in FIG. 2).

  The plate-making writing unit 20 conveys the thermal head 21 in which a plurality of heating elements 21 a are arranged in a line in the main scanning direction and the stencil sheet 23 fed from the stencil sheet roller 22 while pressing the thermal head 21 against the thermal head 21. The platen roller 24 and a base paper transport roller pair 26 that transports the stencil paper 23 made by the thermal head 21 toward the clamp portion 32 of the drum 33 described later. Note that the writing motor 25 indicated by a dotted line in FIG. 2 is a stepping motor and rotationally drives the platen roller 24 and the base paper conveying roller pair 26.

  The cutter unit 30 is a mechanism for cutting the stencil sheet 23. When the stencil sheet 23 made by the thermal head 21 is wound around the drum 33 and has a predetermined length, the stencil sheet 23 is cut. Is provided at a predetermined position.

  Further, the printing unit 40 includes a drum 33 as a rotating part for image transfer that includes an ink supply unit that supplies a predetermined amount of ink to the inner surface of the ink reservoir 58 formed between the doctor roller 56 and the squeegee roller 57, and A primary paper feed roller 46 that picks up and conveys the print paper 43 one by one from the print paper that is stacked on the paper feed tray 44 and forms a copy, and the print paper 43 that is conveyed from the primary paper feed roller 46 A pair of secondary paper feed rollers 42 that are sent out at a timing, a press roller 35 that presses the printing paper 43 fed from the secondary paper feeding roller 42 against the outer peripheral surface of the drum 33, and the printed printing paper 43 is fed into the drum 33. The configuration includes a separation claw 55 for further peeling, and a paper discharge platform 49 for discharging and stacking the print paper 43 peeled off and discharged from the drum 33.

  The printing unit 40 is provided with a paper feed sensor (not shown) and a paper discharge sensor (not shown). The paper feed sensor is a transmission type sensor that detects whether or not the printing paper 43 is conveyed between the secondary paper feeding rollers 42. When the printing paper 43 is detected to be conveyed, a detection signal having a predetermined potential is generated. The data is output to a control unit described later. On the other hand, the paper discharge sensor is a reflective sensor that detects whether or not the print paper 43 is discharged from between the drum 33 and the press roller 35. When it is detected that the print paper 43 is discharged, a predetermined potential is detected. The detection signal is output to the control unit described later. By adding a counter value each time a detection signal is output from the paper discharge sensor, it is possible to count the number of prints of the print paper 43 on which a print image is formed.

  A clamp 32 is provided on the outer peripheral surface of the drum 33 to clamp the leading end of the stencil sheet 23 that has been made and conveyed by the thermal head 21. The pre-made stencil sheet 23 clamped by the clamp part 32 is wound around the outer peripheral surface thereof by rotating the drum 33 (plate making). A main motor 34 indicated by a dotted line in the drawing is a DC motor, and is for driving the drum 33 to rotate. In the following description, the main motor is appropriately referred to as “motor” (reference numeral is omitted). Moreover, in FIG. 2, the code | symbol 41 is a conveyance path.

  An operation panel is provided on the upper surface of the apparatus main body. This operation panel (see FIG. 3) includes a plate making / printing start key 62 for starting plate making and printing processing set in mode, a plate making / printing switch key 66 for switching a plate making / printing mode, and a document mode (character mode). The character mode key 71, the photo mode key 72, and the character / photo mode key 73 for setting the photo mode or the character / photo mode) are arranged. Stop key to stop, reset key to reset items set from the operation panel, numeric keypad to enter the number of copies to be printed, top and bottom position movement amount, setting confirmation key to confirm the selected mode setting, prepress processing A trial printing key for performing trial printing later, a center key for centering the printing position, etc. are arranged. There.

  A display / input panel is arranged on the operation panel. The display / input panel includes a pressure-sensitive or electrostatic transparent touch panel disposed on the front surface and a liquid crystal display panel disposed on the back surface of the touch panel. The user can input various parameters by directly touching the surface of the touch panel with a finger or the like while viewing the display screen of the liquid crystal display panel. For example, when plate making or printing processing is performed, setting of a sorter function, setting of continuous shooting / continuous printing function, and the like can be performed through a setting input screen displayed below the touch panel. In addition to the end of plate making and the start of printing, the liquid crystal display panel also displays a message for notifying the time for motor replacement. Such input means such as various data and settings are not limited to the form of the operation panel exemplified above, and may be in other forms and forms as long as they function in the same manner.

  Next, a functional configuration related to the control system of the stencil printing machine 1 will be described. In FIG. 3, a control unit 81 is a part that controls the operation of the stencil printing machine 1 as a whole, and is configured by a central processing unit (CPU, MPU, etc.) that executes various arithmetic processes and data input / output processes. ing.

  The control unit 81 is connected to a RAM 82 that stores various commands and image information input from the operation panel, and a ROM 83 that stores a control program executed by the control unit 81, and the document reading unit 10 is also connected to the control unit 81. An original reading unit driving circuit 85 to be driven, a plate making / writing unit driving circuit 86 for controlling driving of the plate making / writing unit 20 (punching means), a printing unit driving circuit 87 for controlling driving of the printing unit 40, and the image processing unit 3 are provided. It is connected. Further, a plate making / printing start key 62, a plate making / printing switching key 66, a character mode key 71, a photo mode key 72, a character / photo mode key 73, etc., which are arranged on the operation panel are connected (other connections). The description of the device is omitted).

  A stencil plate making control unit 8 that variably controls the perforated area by adjusting the energy applied to the thermal head 9 (the power supplied to the thermal head 9 or the energization time of the power). It is included in the plate-making writing unit drive circuit 86. The control unit 81, the RAM 82, the ROM 83, an input / output interface (I / O interface) (not shown), and the like can be configured by a microcomputer or the like. However, each of these units can be configured by a plurality of microcomputers, and may be configured as a device that executes a plurality of controls in addition to control of document reading, plate making, printing, and the like.

  Next, processing of the image sensor 11, the A / D conversion unit 89, the image processing unit 4, and the control unit 81 illustrated in FIG. 3 will be described. The image sensor 11 reads the reflected light of the light irradiated on the document, converts the density of the image formed on the document into an analog electric signal by the CCD (photoelectric conversion), and outputs the analog signal to the A / D converter 89.

  The A / D converter 89 converts the analog electrical signal read by the image sensor 11 into, for example, 8-bit (0 to 255 gradation) digital data and outputs the digital data to the image processor 3. At this time, processing such as shading correction is performed. The outline of the processing in the image processing unit 4 is as described above.

  Note that 1-bit monochrome data is represented by “0” or “1” such as “0” for a white pixel, “1” for a black pixel, “1” for a white pixel, and “0” for a black pixel. Digital electrical signal. Further, the pixel pattern handled in this specification will be described. The “solid portion” is a pixel pattern in which black pixels are continuous in the main scanning direction and the sub-scanning direction, and “thin line” is the main scanning direction or the sub-scanning direction. Is a pixel pattern in which black pixels are continuous to each other, “isolated portion” is a pixel pattern in which black pixels are not adjacent in the main scanning direction and the sub-scanning direction, and “halftone region” is the main scanning direction. Or, it is a pixel pattern in which black pixels are scattered in the sub-scanning direction.

  Next, specific examples of the image area determination unit 4 (image area determination unit) and the stencil plate making control unit 8 (perforation control unit), which are the features of the present invention, are [Example 1], [Example 2], This will be described in detail with reference to the drawings, divided into [Modifications].

[Example 1]
First, the image area determination unit 4 and the stencil plate making control unit 8 according to the first embodiment will be described with reference to FIGS. Here, FIG. 4 is a configuration diagram of the image area determination unit 4 of the first embodiment and its surroundings, and FIG. 5 illustrates image area attributes determined by the image area determination unit 4 of the first embodiment according to various signals. 6 is a circuit diagram illustrating the configuration of the thermal head 21, FIG. 7 is a timing chart illustrating various signals for the thermal head 21, and FIG. 8 illustrates three types of determination results (characters, It is explanatory drawing explaining a photograph and intermediate | middle.

  In the first embodiment, the image area determination unit 4 extracts a characteristic indicating the binary image likeness of the image in the image area for the pixel of the image data read by the document reading unit 2 or the image area for each predetermined block (density detection). , Edge detection and distance detection from the edge), and based on the characteristics, the image area attributes are character (binary image), photograph (gradation image), and intermediate (intermediate image of binary image and gradation image) The image area attribute is determined to be an intermediate image, and the image area attributed to the intermediate image is further binarized according to the feature amount (distance detection from the edge) indicating the binary image quality. The image area attributes classified into three stages of the image close to the image, the second intermediate image, and the image closer to the gradation image are determined.

  Further, in the image area whose image area attribute is determined to be a photograph (gradation image) by the stencil plate making control unit 8 (plate making writing unit drive circuit 86), the image area is perforated with a relatively large perforation area (DL). In an image area determined to have an intermediate area attribute (intermediate image of a binary image and a gradation image), the image area attribute is determined to be a character (binary image). In the image area thus formed, the image is perforated with an intermediate perforation area (DM) between the photograph (gradation image) and the middle (intermediate image).

  The image area determination unit 4 according to the first embodiment uses the density of the target pixel, whether or not it is an edge, and the distance of the target pixel from the detected edge as features indicating the likelihood of a binary image. As shown in FIG. 4, a density detection circuit 118, an edge detection circuit 117, and a distance classification circuit 111 are provided.

  The density detection circuit 118 detects the density of the target pixel and validates (enables) the density detection signal when it is greater than or equal to a predetermined threshold, and invalidates (disables) the density detection signal when it is less than the predetermined threshold.

  Further, the edge detection circuit 117 performs a convolution operation using the edge detection coefficient matrix in the horizontal direction, the vertical direction, the left diagonal direction, and the right diagonal direction, and calculates the largest value among the absolute values of the obtained four values. An edge detection signal is validated when the edge signal is equal to or greater than a predetermined edge threshold, and the edge detection signal is invalidated when the edge signal is less than the edge threshold. The dot delay circuit 109 interposed on the output side of the edge detection circuit 117 is an image area by the image area determination circuit 120 at the timing of density conversion of image data to be processed output from the line memory 102 to the density conversion circuit 103. This is to match the output timing of the determination result.

  In addition, when the target pixel is within the first predetermined distance from the edge, the distance classification circuit 111 outputs a distance classification signal = 0, assuming that the image area attribute is a character, and the target pixel is If it is outside the second predetermined distance (which is longer than one predetermined distance), the image area attribute is a photograph and a distance classification signal = 4 is output, and the target pixel is outside the first predetermined distance from the edge and the second If the image area attribute is within the predetermined distance, it is determined that there is a possibility that the image area attribute is in the middle. Further, when the image area attribute is likely to be in the intermediate area, the third pixel is longer than the edge (longer than the first predetermined distance). When the distance is within the predetermined distance, the distance classification signal = 1 is output as there is a possibility that the image area attribute is intermediate (like character), and the target pixel is longer than the second predetermined distance from the edge (longer than the third predetermined distance). (Short) outside the fourth predetermined distance, the image If there is a possibility that the attribute is intermediate (appears to be a photograph), a distance classification signal = 3 is output, and if the target pixel is outside the third predetermined distance and within the fourth predetermined distance from the edge, the image area attribute is The distance classification signal = 2 is output as there is a possibility of being in the middle.

  Further, the image area determination circuit 120 determines the image area attribute of the target pixel based on the density detection signal from the density detection circuit 118, the edge detection signal from the edge detection circuit 117, and the distance classification signal from the distance classification circuit 111. To do. FIG. 5 is a table showing image area attributes (image area determination signals) determined by a combination of these three types of signals. In the figure, “◯” indicates that the signal is valid, “×” indicates that the signal is invalid, and “−” indicates that the signal is valid / invalid or don't care not related to the value. , Respectively.

  The image area attribute of the target pixel is determined to be a character when the edge detection signal is valid or the distance classification signal = 0, and the image area attribute is determined to be a photograph as a distance classification signal. = 4. Furthermore, the image area attribute of the target pixel is determined to be intermediate when the distance classification signal = 1 to 3 and the density detection signal is valid. That is, when the density of the target pixel is equal to or higher than a predetermined threshold, it is determined as “intermediate (character-like)”, “intermediate” or “intermediate (like a photograph)” according to the distance classification signal, and the density of the target pixel is If it is less than the predetermined threshold, the image area attribute is determined as a photograph regardless of the value of the distance classification signal (not shown in FIG. 5).

  The determination result by the image area determination circuit 120 is output as an image area determination signal to the density conversion circuit 103 and a stencil plate making control unit 8 described later. The density conversion circuit 103 performs density conversion by selecting a density conversion curve corresponding to the image area determination signal (image area attribute), and outputs the converted density signal to the binarization circuit 104. The binarization circuit 104 binarizes the input density signal by the error diffusion method and outputs it as a binary signal.

  4 is a modification of the configuration of FIG. 8 in Japanese Patent Laid-Open No. 8-51538, and the configuration of the image area determination unit 4 and its surroundings of the first embodiment shown in FIG. 4 is described in more detail. Please refer to the publication.

  Next, the stencil plate making control unit 8 of Example 1 will be described. FIG. 6 shows the configuration of the thermal head 21 to be controlled by the stencil plate making control unit 8. As shown in FIG. 6, 7168 heating elements 91 of the thermal head 21 are arranged in a line in the main scanning direction. . Each heating element 11 includes 1856 blocks 1 and 4 and 1728 blocks 2 and 3. An AND gate circuit 94 is connected to one end of each lead electrode, and the other end is grounded. Further, a latch unit 95 and a shift register 96 are provided for each block.

  The stencil plate making control unit 8 supplies the clock signals CLK1 to CLK4 and the image data DAT1 to DAT4 for selectively driving the heating element 11 to the thermal head 21 having such a configuration. 96, and latch signals LAT1 to LAT4 are input to the latch circuit 95. Strobe signals STB 1 to STB 4 are input to each AND gate circuit 94.

  When actual punching is performed, first, image data DAT1 to DAT4 are input as serial data to the shift register 96 of the thermal head 21, serial / parallel converted, and latched by the latch unit 95 by latch signals LAT1 to LAT4. The energization control of each heating element 11 is performed by the logical product of the image data DAT1 to DAT4 latched in the latch unit 95 and the strobe signals STB1 to STB4, and the heating element 11 generates heat during energization when the strobe signal is valid. To do.

  The image data DAT1 to DAT4 are composed of black and white data and heat history data for instructing whether or not to perform punching. The input timing of each signal input to each block of the thermal head 21 is divided and driven for each block. Further, since the thermal head 21 of the present embodiment is configured to drive and control by equally dividing into four in this way, the image area to be processed by the image area determination unit 4 of the present embodiment is a block, The block is restricted to a block equally divided into four in the main scanning direction.

  FIG. 7 shows (a) image data DAT (DAT1 to DAT4), (b) latch signal LAT (LAT1 to LAT4), and (c) and (d) strobe signals STB (STB1 to STB4) in four arbitrary blocks. The timing chart is shown. As shown in FIGS. 9A and 9B, the data is supplied to the shift register 96 in order of the black and white data and the thermal history data via the image data DAT, and is supplied to the latch unit 95 at the timing of the trigger pulse of the latch signal LAT. Latched.

  Here, the heat history data is data for performing heat history control. In general, when plate making is performed using a thermal head, if the plate making speed is increased, the next line is made before the heat energy applied to the heating element is sufficiently diffused and released. As a result, the heat energy is accumulated, and as a result, the heat energy corresponding to the past heat generation history is accumulated in each heating element, causing variations in the energy state and image quality degradation. In order to eliminate the image quality deterioration caused by the heat generation history and make the image uniform, the heat history control is based on the past heat generation history (image pattern) of each heating element and the surrounding heating elements. It controls the amount of heat generated by the heating element. In addition, what is necessary is just to apply a well-known technique about the production | generation of heat history data.

  The energy applied to the heating element 91 of the thermal head 21 is applied power (voltage × current) × heating time (power energization time to the heating element 91). In this embodiment, the applied power is constant, the applied energy is adjusted by adjusting the heat generation time, and the perforated area perforated on the stencil sheet is variably controlled.

In the above-described thermal history control, as shown in FIGS. 7C and 7D, the pulse width at which the strobe signal STB is valid (a negative logic signal and valid at “Low”) is relative to the strobe signal STB. A short (tp2) signal STBa and a long (tp1) signal STBb are selected and used according to the image pattern. That is, when the short pulse signal STBa is used for the strobe signal STB, the heating element 91 is heated based on the black and white data for the energization time tp2, while when the long pulse signal STBb is used for the strobe signal STB, the heat generation is generated. The body 91 is heated based on the black and white data and the heat history data for the energization time tp1. (To explain the latter more precisely, heating based on the black and white data is performed until the strobe signal becomes valid and a latch trigger for latching the thermal history data is applied, and a latch trigger for latching the thermal history data is provided. (The heating based on the thermal history data is performed until the strobe signal becomes invalid after being added.)
For example, when the image pattern is solid that is expected to store heat in the heating element, the long pulse signal STBb is used for the first line in the sub-scanning direction, and the short pulse signal STBa is used for the subsequent lines. Further, when the image pattern is an isolated point, control is performed such that the long pulse signal STBb is used.

  Further, in the punching control of the present embodiment, in addition to such thermal history control, the short pulse signal STBa and the long pulse are determined according to the result of the image area determination (image area determination signal) by the image area determination unit 4 of the image processing unit 3. The pulse widths tp2 and tp1 of the signal STBb are variably set.

  Specifically, an image area whose image area attribute is determined to be a character (binary image) is shortened so as to be punched with an intermediate punching area (DM) between a photograph (gradation image) and an intermediate (intermediate image). Assuming that the pulse widths of the pulse signal STBa and the long pulse signal STBb are TP2 and TP1, respectively, an image area whose image area attribute is determined to be a photograph (gradation image) is punched with a relatively large drilling area (DL). Therefore, the pulse widths of the short pulse signal STBa and the long pulse signal STBb are 1.1TP2 to 1.3TP2 and 1.1TP1 to 1.3TP1, respectively. In addition, for an image area whose image area attribute is determined to be intermediate (an intermediate image of a binary image and a gradation image), a short pulse signal STBa and a long pulse signal are to be punched with a relatively small drilling area (DS). The pulse widths of STBb are 0.7TP2 to 0.9TP2 and 0.7TP1 to 0.9TP1, respectively.

  More specifically, for example, for an image area in which the image area attribute is determined to be a character, the pulse width tp2 of the short pulse signal STBa = 380 [μs] and the pulse width tp1 of the long pulse signal STBb = 500 [μs]. For the image area whose image area attribute is determined to be a photograph, the pulse width tp2 of the short pulse signal STBa = 450 [μs], the pulse width tp1 of the long pulse signal STBb = 600 [μs], and the image For the image area in which the area attribute is determined to be intermediate, the pulse width tp2 of the short pulse signal STBa = 300 [μs] and the pulse width tp1 of the long pulse signal STBb = 400 [μs].

  As a method for generating the strobe signal STB, a numerical value corresponding to such a specific value of the pulse width (that is, the pulse width / the length of one cycle of the basic clock used for operation control of the stencil printing apparatus) is prepared in a table. A method of generating a strobe signal STB having a predetermined pulse width by referring to the table according to the thermal history control and the image area attribute, counting the basic clocks corresponding to the numerical values, and the like can be considered.

  When the pulse widths tp2 and tp1 of the short pulse signal STBa and the long pulse signal STBb are variably set at the above ratio according to the image area attribute, the perforation area ratio is as follows: character: intermediate: photograph = 1: 0.7 to 0.9: 1.1 to 1.3.

  As described above, in the stencil plate making apparatus and stencil printing apparatus of this embodiment, the thermal head 21 punches the stencil sheet according to the image area attribute for each predetermined block determined by the image area determination unit 4. Since the perforation area is variably controlled by the stencil plate making control unit 8, local perforation control according to the image area attribute for each image area of the image data can be performed. As a result, the optimum per the original and over the entire original Therefore, it is possible to provide a stencil printing apparatus capable of producing a high-quality printed image faithful to a document.

  In the present embodiment, the image area is divided into four equal blocks in the main scanning direction from the configuration of the thermal head 21, but the present invention is not limited to this, and an arbitrary number (one block on the circuit configuration). (It is desirable that the number of bits is a power of 2), and although the amount of hardware is increased, the image area can be a pixel.

  In this embodiment, the energization time of the power supplied to the thermal head 21 is adjusted in order to variably control the perforation area by adjusting the energy applied to the thermal head 21 by the perforation control unit 8. You may make it adjust with an electric current or these combination.

  In this embodiment, the image area determination unit 4 extracts a feature indicating the binary image likeness of an image in the image area for each image area, and the image area attribute is a character (binary image), a photograph (floor image) based on the feature. Toned image) and intermediate (a binary image and an intermediate image of a gradation image). Here, as the feature information indicating the character (binary image) characteristic, the density of the target pixel, whether it is an edge, and the distance of the target pixel from the detected edge are used, and the LUT method is used based on the feature information. Determine the image area attribute. Thereby, it is possible to accurately determine the image area attribute without erroneous determination.

  Further, in this embodiment, the stencil plate making control unit 8 makes the perforation area relatively larger than that of the binary image when the image area attribute is a gradation image, and when the image area attribute is an intermediate image. Control is performed so that the perforated area is relatively smaller than that of the binary image.

  That is, since an image area whose image area attribute is determined to be a photograph (gradation image) is perforated with a relatively large perforation area (DL), non-occurrence at an isolated point can be prevented. In addition, as illustrated in FIG. 8, even when it is determined to be a photograph, there is a possibility that the image is solid. In the case of solid, it is necessary that the solid part is filled. However, when considering a certain block, since the printing rate is lower in the case of a photo original compared to a character original, the influence of heat from surrounding pixels is small. It is considered that the heat storage in the heating element is small. For this reason, when it is set as a normal or relatively small perforated area, the density of black when viewed as a whole solid portion becomes low. On the other hand, by making the perforation area larger than that at the time of the text document as in this embodiment, a sufficient perforation area can be obtained in the solid portion even if the heat storage of the heating element is small, and when the solid portion is viewed as a whole. The density of black is increased, and a higher quality print image can be obtained.

  Further, since the image area attribute is determined to be intermediate (intermediate image) between the character (binary image) and the photograph (gradation image), the image area is perforated with a relatively small perforation area (DS). The graininess in can be suppressed. That is, as shown in the perforation pattern example of FIG. 8, since black pixels are scattered in the main scanning direction or the sub-scanning direction, if the perforation area of the black pixels is relatively large, the printed image has a graininess (grainy feeling). Will occur. The gradation will not be smooth, but by setting the black pixels to a relatively small perforated area, the graininess of the printed image can be suppressed and the gradation can be smoothed, resulting in a high-quality printed image. Obtainable.

  Further, in the image area in which the image area attribute is determined to be a character (binary image), the image is perforated with an intermediate perforation area (DM) between the photograph (gradation image) and the middle (intermediate image), so that the solid portion is uniform. The top / end difference in the sub-scanning direction at the solid portion can be suppressed. As illustrated in FIG. 8, there is a possibility that an isolated point may be an isolated point even if it is determined as a character, but normally, an isolated point existing in a highlight portion or the like of a document has a high probability of being determined as a photograph. The probability of being judged as a character is low. Therefore, even if the attribute is an intermediate perforated area in the character image area, the probability that an isolated point will not occur is low and there is no problem. In this manner, local punching control can be performed according to the image area attribute for each image area of the image data, and as a result, an optimum stencil can be created according to the original and over the entire original.

  In this embodiment, the stencil plate making control unit 8 determines the determined image area attributes, that is, characters (binary image), photograph (gradation image), and intermediate (intermediate image of binary image and gradation image). Although the perforation area is variably controlled according to the image area, the image area determination unit 4 uses more characters (binary image) for the image area in which the image area attribute is determined to be intermediate (intermediate image of the binary image and the gradation image). Image area attributes classified into three levels between images closer to the image and images closer to the photo (gradation image) are determined. From the characters (binary image), the photo (gradation image), and the binary image The perforation area may be variably controlled according to the image area attributes of all five stages of the intermediate image, the intermediate image from the gradation image, and the second intermediate image.

  For example, in order to variably control the perforation area by adjusting the energy applied to the thermal head 21 by the perforation control unit 8, when adjusting by the voltage applied to the thermal head 21, the perforation area S [μm 2 by the predetermined voltage V ], A perforation area of 0.60 to 0.85 × S is obtained at a voltage of 0.9 × V, and a perforation area of 0.85 to 0.95 × S is obtained at a voltage of 0.95 × V. As a result, a perforation area of 1.05 to 1.15 × S is obtained at a voltage of 1.05 × V, and a perforation area of 1.15 to 1.40 × S is obtained at a voltage of 1.1 × V. With reference to such simulation experiment results, control amounts for all five stages of image area attributes may be determined and variably controlled.

  As a result, the difference between the perforated areas is gradually filled at the boundary between the image area of the binary image and the image area of the intermediate image and the boundary between the image area of the intermediate image and the image area of the gradation image. And local drilling control can be performed more finely.

  Furthermore, in this embodiment, as shown in FIG. 4, the image processing unit 3 (the image area determination unit 4, the density conversion unit 5, and the halftone processing unit 6) is configured by a circuit. However, the present invention is not limited to this. You may implement | achieve as a program run on processors, such as MPU or DSP.

[Example 2]
Next, the image area determination unit 4 and the stencil plate making control unit 8 according to the second embodiment will be described with reference to FIGS. 9 and 10. Here, FIG. 9 is a configuration diagram of the image area determination unit 4 of the second embodiment, and FIG. 10 is an explanatory diagram for explaining image area attributes determined by the image area determination unit 4 of the second embodiment according to various signals. It is.

  In the second embodiment, the image area determination unit 4 extracts a feature indicating the binary image likeness of the image in the image area for the pixel of the image data read by the document reading unit 2 or the image area for each predetermined block (thin line detection). High density line detection, edge detection and distance detection from the edge), and based on the characteristics, the image area attribute is any of a binary image, a gradation image, and an intermediate image of the binary image and the gradation image. An image closer to a binary image according to a feature quantity (distance detection from an edge) indicating the likelihood of a binary image for an image area whose image area attribute is determined to be an intermediate image. The image area attributes classified into the three stages of the second intermediate image and the image closer to the gradation image are determined.

  In addition, the image stencil making control unit 8 perforates with a relatively large perforation area (DL) in the image area in which the image area attribute is determined to be a gradation image, and the image area in which the image area attribute is determined to be a binary image. In the image area in which the image area attribute is determined to be the second intermediate image, the above-described relatively small area (DS) In addition, in the image area in which the image area attribute is determined to be an intermediate image from the binary image, the perforated area (DM) when the image area attribute is the binary image and the perforated area (DS) when the image area attribute is the second intermediate image And an image area in which the image area attribute is determined to be an intermediate image from the gradation image, and the second perforation area (DL) and the second area when the image area attribute is the gradation image. In the case of the intermediate image, a hole is drilled at a hole area (DS2) intermediate to the hole area (DS).

  In the image area determination unit 4 according to the second embodiment, the characteristics indicating the binary image quality include a thin line, a high density line, an edge, and a detected edge. The distance of the target pixel is used, and a thin line detection circuit 105, a high density line detection circuit 110, an edge detection circuit 107, and a distance classification circuit 111 are provided as shown in FIG.

  In the fine line detection circuit 118, the convolution calculation is performed by the fine line detection coefficient matrix in the horizontal direction (main scanning direction) and the vertical direction (sub-scanning direction), and the largest value of the absolute values of the two obtained values is obtained. A fine line signal is made valid when the fine line signal is equal to or greater than a predetermined fine line threshold, and invalid when it is less than the fine line threshold. Note that the dot delay circuit 106 interposed on the output side of the thin line detection circuit 105 has an image area by the image area determination circuit 121 at the timing of density conversion of image data to be processed output from the line memory 102 to the density conversion circuit 103. This is to match the output timing of the determination result.

  Further, the edge detection circuit 107 performs a convolution operation using the edge detection coefficient matrix in the horizontal direction, the vertical direction, the left diagonal direction, and the right diagonal direction, and calculates the largest value among the absolute values of the obtained four values. The edge signal is compared with the first and second edge thresholds.

  The first edge threshold is set to a value that can detect only a sharp (large density difference) edge that hardly appears in the gradation image. When the edge signal is greater than or equal to the first edge threshold, the first edge detection signal is When it is valid and is less than the first edge threshold, the first edge detection signal is invalidated. The second edge threshold is set to a value that is smaller than the first edge threshold and is capable of detecting a slightly sharp edge (slightly large density difference), and when the edge signal is equal to or greater than the second edge threshold. Is enabled, and the second edge detection signal is disabled when it is less than the second edge threshold.

  The high density line detection circuit 110 is a circuit used to recognize a line having a preset size and density, and the target pixel is sandwiched between a rising edge image and a falling edge image, and Whether or not the density is high is detected and a high density line detection signal is output.

  In addition, when the target pixel is within the first predetermined distance from the edge, the distance classification circuit 111 outputs a distance classification signal = 0, assuming that the image area attribute is a character, and the target pixel is If it is outside the second predetermined distance (which is longer than one predetermined distance), the image area attribute is a photograph and a distance classification signal = 4 is output, and the target pixel is outside the first predetermined distance from the edge and the second If the image area attribute is within the predetermined distance, it is determined that there is a possibility that the image area attribute is in the middle. Further, when the image area attribute is likely to be in the intermediate area, the third pixel is longer than the edge (longer than the first predetermined distance). When the distance is within the predetermined distance, the distance classification signal = 1 is output as there is a possibility that the image area attribute is intermediate (like character), and the target pixel is longer than the second predetermined distance from the edge (longer than the third predetermined distance). (Short) outside the fourth predetermined distance, the image If there is a possibility that the attribute is intermediate (appears to be a photograph), a distance classification signal = 3 is output, and if the target pixel is outside the third predetermined distance and within the fourth predetermined distance from the edge, the image area attribute is The distance classification signal = 2 is output as there is a possibility of being in the middle.

  Further, in the image area determination circuit 121, the density detection signal from the thin line detection circuit 105, the first and second edge detection signals from the edge detection circuit 107, the high density line detection signal from the high density line detection circuit 110, and Based on the distance classification signal from the distance classification circuit 111, the image area attribute of the target pixel is determined. FIG. 10 is a table showing image area attributes (image area determination signals) determined by a combination of these five types of signals. In the figure, “◯” indicates that the signal is valid, “×” indicates that the signal is invalid, and “−” indicates that the signal is valid / invalid or don't care not related to the value. , Respectively.

  The image area attribute of the target pixel is determined to be a character when the thin line detection signal is valid, when the high density line detection signal is valid, when the first edge detection signal is valid, or when the distance classification signal is = 0 and the image area attribute is determined to be a photograph when the distance classification signal = 4. Furthermore, the image area attribute of the target pixel is determined to be intermediate when the distance classification signal = 1 to 3. That is, it is determined as “intermediate (character-like)”, “intermediate” or “intermediate (like a photo)” according to the distance classification signal.

  The configuration of the image area determination unit 4 and its surroundings according to the second embodiment shown in FIG. 9 is a modification of the configuration of FIG. 12 in Japanese Patent Application Laid-Open No. 8-51538, and more detailed description of each component. Please refer to the publication.

  Next, the stencil plate making control unit 8 of the second embodiment may be carried out in substantially the same manner as the first embodiment, and detailed description thereof is omitted. In the second embodiment, the energization time of the electric power supplied to the thermal head 21 by the perforation control unit 8 is adjusted according to the image region attributes of all five stages for each predetermined block determined by the image region determination unit 4. However, the setting of the energization time according to the three-step image area attributes in the intermediate (intermediate image) may be set in accordance with the first embodiment.

  As described above, in the stencil plate making apparatus and stencil printing apparatus of this embodiment, the thermal head 21 punches the stencil sheet according to the image area attribute for each predetermined block determined by the image area determination unit 4. Since the punching area is variably controlled by the stencil plate making control unit 8, as in the first embodiment, local punching control according to the image area attribute for each image area of the image data can be performed. In addition, it is possible to provide a stencil plate making apparatus capable of producing an optimum stencil over the entire original, and to provide a stencil printing apparatus capable of realizing a high-quality printed image faithful to the original.

  Further, in this embodiment, the image area determination unit 4 extracts a characteristic indicating the binary image likeness of the image in the image area for each image area, and based on the feature, the image area attribute is any of the five levels of attributes. It is determined whether it is. Here, as feature information indicating the character (binary image) characteristic, whether it is a thin line, whether it is a high density line, whether it is an edge, and the distance of the target pixel from the detected edge The image area attribute is determined by the LUT method based on the feature information. Thereby, it is possible to accurately determine the image area attribute without erroneous determination.

  Further, in this embodiment, as shown in FIG. 9, the image processing unit 3 (the image area determination unit 4, the density conversion unit 5, and the halftone processing unit 6) is configured by a circuit. However, the present invention is not limited to this. You may implement | achieve as a program run on processors, such as MPU or DSP.

[Modification]
In the first and second embodiments described above, the pixel of the input image data or the image area of each predetermined block is classified in multiple stages between the binary image and the gradation image by the image area determination unit 4. Since the perforated area is variably controlled according to the image area attribute by the stencil plate making control unit 8, the character mode key 71, the photograph in the configuration of the embodiment is inherently determined. It is not necessary to set the original mode (character mode, photo mode or character / photo mode) by the mode key 72 or the character / photo mode key 73, and an optimum stencil can be created even if the user setting is not required, and the original is faithfully reproduced. The fact that a high-quality printed image can be realized is also a characteristic effect of the present invention.

  However, on the other hand, the setting of the document mode (character mode, photo mode, or character / photo mode) is applied to a wide variety of stencil printing apparatuses currently used because of the necessity of appropriately selecting a density conversion curve. This modification is proposed as a technique for applying the present invention to a stencil printing apparatus having such a document mode setting function.

  That is, in this modification, a character mode that performs a printing operation according to a character image, a photo mode that performs a printing operation according to a photographic image, and a printing according to a mixed image such as a character image and a photographic image. A mode setting means for setting a character / photo mode for operation (in the above embodiment, a character mode key 71, a photo mode key 72 or a character / photo mode key 73 on the scanning panel), and a character mode by the mode setting means The reference control amount given to the thermal head 21 for punching with the punching area (DM) when the image area attribute is character (binary image) in the stencil plate making control unit 8 according to the setting of the photo mode or the character / photo mode. Is variable. Here, the reference control amounts are the pulse widths tp2 and tp1 of the short pulse signal STBa and the long pulse signal STBb used for the strobe signal STB when the image area attribute is character (binary image) in the first embodiment. .

  For example, when the character mode is set, a reference control amount that sets a larger punching area than when the character / photo mode is set is set, and when the photo mode is set, a reference control amount that sets a smaller punching area than when the character / photo mode is set. That is, the perforated area is “when character mode is set> when character / photo mode is set> when photo mode is set”.

  As described above, the reference control amount is made variable according to the setting of the document mode (character mode, photo mode or character / photo mode), the reference control amount suitable for each document is set, and the image area of the image data is further set. By performing local punch control according to each image area attribute, the punch control amount is set in two stages, and finer punch control can be performed. It is possible to provide a stencil printing apparatus that can create a more optimal stencil over the entire original and can realize a high-quality printed image faithful to the original.

  Further, as another modification, mode setting means is provided so that when the character mode is set, the punching area is larger than when the character / photo mode is set. When the photo mode is set, the punching area is smaller than that when the character / photo mode is set. It is conceivable to adjust the energy applied to the thermal head so that the punching control of the first or second embodiment is performed only when the character / photo mode is set. The problem described in “Problems to be Solved by the Invention” is particularly noticeable when the character / photo mode is set.

  In the above description, the stencil printing apparatus is provided with the document reading unit 2, and the image area attribute determination is performed by the image region determination unit 3 on the image data input from the document reading unit 2. However, the present invention is not limited to this configuration. For example, the stencil plate making apparatus or the stencil printing apparatus may be connected to the network and may process image data input by communication through the network. Further, the present invention is not limited to communication via the network, and may be configured to input digital image data recorded on a predetermined electronic recording medium via a predetermined interface.

DESCRIPTION OF SYMBOLS 1 ... Stencil printing machine 2 ... Original reading part 3 ... Image processing part 4 ... Image area determination part (image area determination means)
DESCRIPTION OF SYMBOLS 5 ... Density conversion part 6 ... Halftone processing part 7 ... Document 8 ... Punching plate making control part 10 ... Document reading part 11 ... Image sensor 20 ... Plate making writing part 21 ... Thermal head 21a ... Heat generating body 23 ... Stencil paper 33 ... Drum DESCRIPTION OF SYMBOLS 40 ... Printing part 43 ... Printing paper 60 ... Operation panel 62 ... Plate making / printing start key 66 ... Plate making / printing switching key 70 ... Touch panel 71 ... Character mode key 72 ... Photo mode key 73 ... Text / photo mode key 81 ... Control part 82 ... RAM
83 ... ROM
85: Document reading unit driving circuit 86 ... Plate making / writing unit driving circuit 87 ... Printing unit driving circuit 89 ... A / D conversion unit 94 ... AND gate circuit 95 ... Latch circuit 96 ... Shift register 102 ... Line memory 103 ... Density conversion circuit DESCRIPTION OF SYMBOLS 105 ... Fine line detection circuit 107,117 ... Edge detection circuit 110 ... High density line detection circuit 111 ... Distance classification circuit 118 ... Density detection circuit 120, 121 ... Image area determination circuit

Claims (10)

Image area determination means for determining image area attributes classified into multi-stages between a binary image and a gradation image for the pixel of the input image data or the image area for each predetermined block;
Perforating means for forming a perforated image on the stencil sheet based on the image data;
Perforation control means for variably controlling a perforation area perforated on the stencil sheet by the perforation means according to the image area attribute determined by the image area determination means;
A stencil plate making apparatus comprising: The punching means has a thermal head in which a plurality of heating elements are arranged in the main scanning direction, and each heating element of the thermal head is selectively heated to form a punched image on the stencil sheet based on the image data. That form
The stencil plate making apparatus according to claim 1, wherein the punching control unit variably controls a punching area by adjusting energy applied to the thermal head.   3. The stencil making apparatus according to claim 2, wherein the punching control unit variably controls a punching area by adjusting an electric power supplied to the thermal head or an energization time of the power.   The image area determination means extracts a feature indicating the likelihood of a binary image of an image in the image area for each image area, and based on the feature, the image area attribute is a binary image, a gradation image, and a binary image and The stencil plate making apparatus according to any one of claims 1 to 3, wherein it is determined which of the intermediate images of the gradation image is.   When the image area attribute is an intermediate image, the perforation control means is more than when the image area attribute is a gradation image, so that the perforation area is relatively larger than that in the case of a binary image. The stencil plate making apparatus according to claim 4, wherein the stencil plate making apparatus is controlled so as to have a relatively small perforated area.   The image area determination means is closer to a binary image according to a feature amount indicating the characteristic of the binary image for an image area whose image area attribute is determined to be an intermediate image between a binary image and a gradation image. 6. The stencil plate making apparatus according to claim 4, wherein image area attributes classified into multiple stages between images closer to a gradation image are determined. Character mode for performing printing operations according to character images, etc., Photo mode for performing printing operations according to photographic images, etc., and character / photo mode for performing printing operations according to mixed images such as character images and photographic images Mode setting means for setting
The punching control unit makes a control amount (hereinafter referred to as a reference control amount) given to the punching unit variable when the image area attribute is a binary image according to the setting of the mode setting unit. The stencil plate making apparatus according to any one of claims 4 to 6.   The punching control means sets a reference control amount that provides a larger punching area than when the text / photo mode is set when the character mode is set by the mode setting means, and is smaller than when the text / photo mode is set when the photo mode is set. 8. The stencil plate making apparatus according to claim 7, wherein a reference control amount to be a piercing area is set.   A stencil printing apparatus comprising the stencil plate making apparatus according to any one of claims 1 to 8. A document reading means;
The stencil printing apparatus according to claim 9, wherein the image area determination unit performs image area attribute determination on the image data input from the document reading unit.

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