JP2012133036A - Image forming apparatus and calculation method for toner amount - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately calculate an amount of consumed toner.SOLUTION: A filter part 41 performs a filter operation in which an edge in image data may be detected. A toner amount calculation part 42 derives an amount of consumed toner on the basis of basic data values obtained by adding filter output values of the filter part 41 to a pixel value of a target pixel. The filter part 41 calculates the filter output values on the basis of pixel values of pixels disposed around the target pixel and involved in a window of a prescribed size, and the window covers a range of a maximum distance from the target pixel at which the target pixel may be affected by an edge effect.

Description

  The present invention relates to an image forming apparatus and a toner amount calculation method.

  An electrophotographic image forming apparatus such as a printer or a multifunction peripheral forms an image by taking out toner from a toner cartridge. Some of such electrophotographic image forming apparatuses measure toner consumption. Usually, the toner consumption is indirectly measured from image data or the like.

  In an electrophotographic image forming apparatus, an electrostatic latent image is formed on a photosensitive drum or the like. An edge electric field is generated at the boundary between the dot-exposed portion and the dot-free portion of the electrostatic latent image, and toner is consumed more than necessary. This phenomenon is called an edge effect. For this reason, various methods for deriving the toner consumption in consideration of the edge effect have been proposed.

  In the apparatus described in Patent Document 1, the target pixel is moved in the image, the number of times the edge is detected in the target pixel is counted, and the toner consumption amount is derived based on the number of edges and the pixel value of the image. .

JP-A-6-175500

  In the apparatus described in Patent Document 1 described above, an edge is detected in consideration of only peripheral pixels whose distance from the target pixel is one pixel. However, since the edge effect in the electrostatic latent image also affects pixels that are two or more pixels away, there is a possibility that the toner consumption amount may not be accurately calculated.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a toner amount calculation method in which a toner consumption amount is accurately calculated.

  In order to solve the above problems, the present invention is configured as follows.

  An image forming apparatus according to the present invention includes a filter unit capable of detecting an edge in image data, and a toner consumption amount based on a basic data value obtained by adding a filter output value of the filter unit to a pixel value of a target pixel. A toner amount deriving unit for deriving toner. Then, the filter unit calculates a filter output value from the pixel values of pixels around the target pixel that fall within a window of a predetermined size, and the window has a maximum distance that gives an edge effect to the target pixel from the target pixel. Includes range.

  Thus, the toner consumption amount can be accurately calculated even when there is an influence of the edge effect from a pixel that is two pixels or more away from the target pixel.

  In addition to the image forming apparatus described above, the image forming apparatus according to the present invention may be configured as follows. In this case, the filter unit outputs a plurality of filter outputs for the pixel values of the surrounding pixels at the distance from the target pixel for each distance from the target pixel to a maximum distance that gives an edge effect to the target pixel. Calculate the value. The toner amount deriving unit derives the toner consumption amount based on the basic data value obtained by adding the plurality of filter output values calculated for each distance by the filter unit to the pixel value of the target pixel.

  As a result, the influence of the edge effect is finely considered according to the distribution state of the dots, and the toner consumption amount is accurately calculated.

  The image forming apparatus according to the present invention may be configured as follows in addition to any of the image forming apparatuses described above. In this case, the toner amount deriving unit performs the first calculation result by the filter unit on the pixel values of the peripheral pixels whose distance from the target pixel is (n−1) pixels, and the peripheral pixels whose distance from the target pixel is n pixels. The value of the first calculation result based on the second calculation result by the filter unit for the pixel value and the third calculation result by the filter unit for the pixel value of the peripheral pixel whose distance from the target pixel is (n + 1) pixels When the value of the second calculation result is lower than both the value of the third calculation result and the value of the third calculation result, the basic data value is derived without adding the second calculation result to the pixel value of the target pixel.

  As a result, a situation where the influence of the edge effect is reduced, such as when pixels without dots are not continuous, is taken into account, and the toner consumption amount is accurately calculated.

  The image forming apparatus according to the present invention may be configured as follows in addition to any of the image forming apparatuses described above. In this case, the toner amount deriving unit sets the pixel value of the target pixel as the basic data value when the pixel values of all the peripheral pixels whose distance from the target pixel is one pixel are zero.

  As a result, it is considered that the toner consumption does not increase due to the edge effect for the isolated dots, and the toner consumption amount is accurately calculated.

  The image forming apparatus according to the present invention may be configured as follows in addition to any of the image forming apparatuses described above. In this case, the filter unit is a Laplacian filter.

  The toner amount calculation method according to the present invention includes a step of calculating a filter output value for a peripheral pixel of a pixel value of a target pixel with a filter capable of detecting an edge in image data, and the filter output value as a pixel of the target pixel. Deriving the toner consumption based on the basic data value obtained by adding to the value. Further, the filter calculates a filter output value from the pixel values of pixels around the target pixel that fall within a window of a predetermined size. The window includes a range of a maximum distance that gives an edge effect to the target pixel from the target pixel.

  Thus, the toner consumption amount can be accurately calculated even when there is an influence of the edge effect from a pixel that is two pixels or more away from the target pixel.

  According to the present invention, the toner consumption is accurately calculated.

FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a diagram illustrating a specific example of the filter unit in FIG. FIG. 4 is a diagram illustrating an example of distribution of basic data values by the filter unit and the toner amount calculation unit in FIG. FIG. 5 is a diagram showing an example of an actual measurement result showing the relationship between the width of the region with dots and the width of the region without dots and the edge effect (toner consumption). FIG. 6 is a diagram illustrating a specific example of the filter unit in the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.

  FIG. 1 is a side view showing a part of a mechanical internal configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus is an apparatus having an electrophotographic printing function, such as a printer, a facsimile machine, a copying machine, or a multifunction machine.

  The image forming apparatus of this embodiment has a tandem color developing device. The color developing device includes photosensitive drums 1a to 1d, an exposure device 2, and developing units 3a to 3d. The photoconductor drums 1a to 1d are four-color photoconductors of cyan, magenta, yellow, and black. The photosensitive drums 1a to 1d are made of amorphous silicon, for example.

  The exposure apparatus 2 is an apparatus that forms an electrostatic latent image by irradiating the photosensitive drums 1a to 1d with laser light while scanning. The laser beam is scanned in a direction (main scanning direction) perpendicular to the rotation direction (sub-scanning direction) of the photosensitive drums 1a to 1d. The exposure apparatus 2 has a laser scanning unit including a laser diode that is a light source of laser light and optical elements (lenses, mirrors, polygon mirrors, etc.) that guide the laser light to the photosensitive drums 1a to 1d.

  Further, around the photosensitive drums 1a to 1d, a charger such as a scorotron, a cleaning device, a static eliminator and the like are arranged. The cleaning device removes residual toner on the photosensitive drums 1a to 1d after the primary transfer, and the static eliminator neutralizes the photosensitive drums 1a to 1d after the primary transfer.

  The developing units 3a to 3d attach the toner cartridge filled with toners of four colors of cyan, magenta, yellow and black, and the toner conveyed from the toner hopper in the toner cartridge to the photosensitive drums 1a to 1d. A developing unit, and the toner is attached to the electrostatic latent images on the photosensitive drums 1a to 1d to form a toner image.

  The photosensitive drum 1a and the developing unit 3a develop magenta, the photosensitive drum 1b and the developing unit 3b develop cyan, and the photosensitive drum 1c and the developing unit 3c develop yellow. Then, black development is performed by the photosensitive drum 1d and the developing unit 3d.

  The intermediate transfer belt 4 is an annular image carrier (intermediate transfer member) that comes into contact with the photosensitive drums 1a to 1d and primarily transfers the toner images on the photosensitive drums 1a to 1d. The intermediate transfer belt 4 is stretched around the driving roller 5 and circulates in the direction from the contact position with the photosensitive drum 1d to the contact position with the photosensitive drum 1a by the driving force from the driving roller 5.

  The transfer roller 6 brings the conveyed paper into contact with the intermediate transfer belt 4 and secondarily transfers the toner image on the intermediate transfer belt 4 to the paper. The sheet on which the toner image has been transferred is conveyed to the fixing device 9 and the toner image is fixed on the sheet.

  The roller 7 has a cleaning brush, and the cleaning brush is brought into contact with the intermediate transfer belt 4 to remove the toner remaining on the intermediate transfer belt 4 after the transfer of the toner image onto the paper.

  The sensor 8 irradiates the intermediate transfer belt 4 with a light beam, and detects reflected light from the surface of the intermediate transfer belt 4 or a toner pattern on the surface. For example, the sensor 8 irradiates a predetermined region of the intermediate transfer belt 4 with light when detecting toner density, detects reflected light of the light, and outputs an electrical signal corresponding to the amount of light.

  FIG. 2 is a block diagram showing a part of the electrical configuration of the image forming apparatus according to the embodiment of the present invention. As illustrated in FIG. 2, the image forming apparatus includes a communication device 11, an arithmetic processing device 12, and a printing device 13.

  The communication device 11 can be connected to a host device via a network or a peripheral device interface, and performs data communication using a predetermined communication protocol.

  The arithmetic processing unit 12 is a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. Various processing units are realized by executing the program by the CPU.

  The printing apparatus 13 is an internal device that prints a document image on paper with a mechanical configuration as shown in FIG.

  After the image forming apparatus is activated, various programs are appropriately executed by the arithmetic processing unit 12. In this embodiment, the arithmetic processing unit 12 implements processing units such as an operating system (not shown), a communication processing unit 21, a print request processing unit 22, an image processing unit 23, a controller 24, and a toner consumption calculation unit 25. The

  The communication processing unit 21 is a processing unit that controls the communication device 11 to execute data communication with a host device or the like. For example, the communication processing unit 21 receives document data as a print request from the host device.

  The print request processing unit 22 receives a print request based on a user operation on the operation panel or a print request supplied from the host device, and executes a print job corresponding to the request. For example, when document data in a predetermined data format such as PDL (Page Description Language) or PDF (Portable Document Format) is received as a print request from the host device, the print request processing unit 22 reads image data from the document data. Is generated. This image data is bitmap data, and when the original data of bitmap data is received from the host device, the print request processing unit 22 uses the original data as image data as it is.

  The image processing unit 23 executes predetermined image processing on the image data, and generates print data (for example, print image data binarized for each color).

  The controller 24 is a processing unit that monitors and controls an internal device such as the printing apparatus 13. The controller 24 controls an unillustrated drive source for driving the above-described roller, a bias application circuit for applying a development bias and a primary transfer bias, and the exposure device 2 to develop, transfer and fix a toner image, and It is a processing circuit for executing paper feeding, printing, and paper ejection. The developing bias is applied between the photosensitive drums 1a to 1d and the developing units 3a to 3d, respectively, and the primary transfer bias is applied between the photosensitive drums 1a to 1d and the intermediate transfer belt 4, respectively.

  In addition, the toner consumption calculation unit 25 calculates the toner consumption associated with printing by the printing device 13. Further, the toner consumption calculation unit 25 calculates the remaining amount of toner in the toner cartridge from the toner consumption. Further, the toner consumption amount calculation unit 25 displays the integrated value of the toner consumption amount and the remaining toner amount on an operation panel (not shown), or displays a warning message on the operation panel (not shown) when the remaining toner amount is low. Display.

  The toner consumption amount calculation unit 25 includes a filter unit 41 and a toner amount calculation unit 42.

  The filter unit 41 is a filter similar to the edge detection filter. The filter unit 41 calculates a filter output value from the pixel values of pixels around the target pixel that fall within a window of a predetermined size. The window has a size including the range of the maximum distance that gives an edge effect to the target pixel from the target pixel. That is, the window includes all the pixels within the maximum distance before and after the main scanning direction and within the maximum distance before and after the sub-scanning direction with the target pixel as the center. For this reason, when the maximum distance is 3 pixels, the size of the window is 7 × 7. In this embodiment, the filter unit 41 is a Laplacian filter. The “distance” here is a value obtained by adding 1 to the number of pixels existing between two pixels. That is, the distance between adjacent pixels is 1.

  The toner amount calculation unit 42 calculates the toner consumption amount based on the basic data value obtained by adding the filter output value of the filter 41 unit to the pixel value of the target pixel.

  In this embodiment, for each distance from the distance of 1 from the target pixel to the maximum distance that gives an edge effect to the target pixel, the filter unit 41 applies the pixel values of the surrounding pixels at the distance from the target pixel. Calculate multiple filter output values. The toner amount calculation unit 42 derives a toner consumption amount based on a value obtained by adding the plurality of filter output values calculated for each distance by the filter unit 41 to the pixel value of the target pixel.

  The toner amount calculation unit 42 performs the first calculation result by the filter unit 41 on the pixel values of the peripheral pixels whose distance from the target pixel is (n−1) pixels, and the peripheral where the distance from the target pixel is n pixels. Based on the second calculation result by the filter unit 41 with respect to the pixel value of the pixel and the third calculation result by the filter unit 41 with respect to the pixel value of the peripheral pixel whose distance from the target pixel is (n + 1) pixels When the value of the second calculation result is lower than both the value of the result and the value of the third calculation result, the toner amount is derived without adding the second calculation result to the pixel value of the target pixel. . Note that n is an integer of 2 or more.

  Further, when the pixel values of all the pixels whose distance from the target pixel is one pixel are zero, the toner amount calculation unit 42 sets the pixel value of the target pixel as the basic data value.

  Next, the operation of the image forming apparatus will be described.

  The filter unit 41 moves the target pixel in the image data after the screen processing, and calculates a filter output value for each pixel. Then, the toner amount calculation unit 42 calculates the toner consumption amount for each pixel based on the filter output value, and sets the sum of them as the toner consumption amount at the time of printing the image based on the image data.

  Hereinafter, specific calculation of the toner consumption amount for the target pixel will be described.

  FIG. 3 is a diagram illustrating a specific example of the filter unit 41 in FIG. FIG. 3A is a diagram illustrating an example of the window of the filter unit 41. FIG. 3B is a diagram illustrating an example of the filter coefficient of the filter unit 41.

  This window is for the case where the maximum distance that gives the edge effect to the pixel of interest is 3 pixels. Therefore, as shown in FIG. 3A, this window is a 7 × 7 pixel window in which the target pixel X is the center.

  As shown in FIG. 3, for the peripheral pixels A1, B1, C1, and D1 that are at a distance of one pixel from the target pixel X in the main scanning direction and the sub-scanning direction, the filter unit 41 sets the distance from the target pixel X to one pixel. A value S1 of the first calculation result indicating the influence from a certain peripheral pixel is calculated according to the following equation.

  S1 = k {4X- (A1 + B1 + C1 + D1)}

  However, k is a predetermined enhancement coefficient, X is the pixel value of the target pixel X, and A1, B1, C1, and D1 are the pixel values of the peripheral pixels A1, B1, C1, and D1. If S1 <0, S1 = 0.

  Further, as shown in FIG. 3, for the peripheral pixels A2, B2, C2, and D2 that are at a distance of two pixels from the target pixel X in the main scanning direction and the sub-scanning direction, the filter unit 41 includes two pixels from the target pixel X. A value S2 of the second calculation result indicating the influence from surrounding pixels at the distance is calculated according to the following equation.

  S2 = k {4X- (A2 + B2 + C2 + D2)}

  However, k is a predetermined enhancement coefficient, X is the pixel value of the target pixel X, and A2, B2, C2, and D2 are pixel values of the peripheral pixels A2, B2, C2, and D2. If S2 <0, S1 = 0.

  Further, as shown in FIG. 3, for the peripheral pixels A3, B3, C3, and D3 that are at a distance of three pixels from the target pixel X in the main scanning direction and the sub-scanning direction, the filter unit 41 includes three pixels from the target pixel X. A value S3 of the third calculation result indicating the influence from surrounding pixels at the distance is calculated according to the following equation.

  S3 = k {4X- (A3 + B3 + C3 + D3)}

  Here, k is a predetermined enhancement coefficient, X is the pixel value of the target pixel X, and A3, B3, C3, and D3 are pixel values of the peripheral pixels A3, B3, C3, and D3. If S3 <0, S1 = 0.

  Further, when S2 <S1 and S2 <S3, S2 = 0.

  The toner amount calculation unit 42 adds the above-described first to third calculation result values S1, S2, and S3 to the pixel value X of the target pixel, and calculates the basic data value X1 (= X + S1 + S2 + S3) of the target pixel. To do. However, when the pixel values of the peripheral pixels E, F, G, H, A1, B1, C1, and D1 of the target pixel are all zero (that is, no dots), the toner amount calculation unit 42 determines the target pixel. Let the pixel value X be the basic data value X1 (= X) of the pixel of interest.

  FIG. 4 is a diagram illustrating an example of the distribution of basic data values by the filter unit 41 and the toner amount calculation unit 42 in FIG. FIG. 4 shows the distribution of basic data values for a solid character image of “OP”, where the gray portion has a value of 1, and the value increases as it approaches black. As shown in FIG. 4, the basic data value of the edge portion is larger than the inside of the character, and the distribution matches the distribution tendency of the toner consumption.

  The toner amount calculation unit 42 calculates the toner consumption amount for the pixel from the basic data value X1. At this time, the conversion from the basic data value X1 to the toner consumption amount is performed by a look-up table or a function expression obtained by experiments or the like.

  Note that the maximum distance that gives the edge effect to the pixel of interest is measured, for example, as follows.

  FIG. 5 is a diagram showing an example of an actual measurement result showing the relationship between the width of the region with dots and the width of the region without dots and the edge effect (toner consumption). FIG. 5B shows a toner when a dot-exposed area having a width X that extends in the sub-scanning direction is printed at an interval Y (that is, sandwiching an area without a dot having a width Y) as shown in FIG. Indicates consumption. The values in FIG. 5B indicate the ratio of the toner consumption amount per unit area when printing is performed under each condition (X, Y) with respect to the toner consumption amount per unit area of the whole surface solid coating. As shown in FIG. 5B, when the continuous number of pixels without dots (that is, the width of the dotless region) is 4 or more, the toner consumption per unit area does not change. The maximum distance affected by the edge effect is specified to be 3 pixels. As described above, the maximum distance affected by the edge effect is specified from the actual measurement result in the same process environment as the image forming apparatus, and the filter unit 41 having a window having a size corresponding to the maximum distance is used.

  As described above, according to the first embodiment, the filter unit 41 performs a filter operation that can detect an edge in image data. The toner amount calculation unit 42 derives the toner consumption amount based on the basic data value obtained by adding the filter output value of the filter unit 41 to the pixel value of the target pixel. Then, the filter unit 41 calculates a filter output value from the pixel values of pixels around the target pixel that fall within a window of a predetermined size, and the window is the maximum distance that gives an edge effect to the target pixel from the target pixel. Including the range.

  Thus, the toner consumption amount can be accurately calculated even when there is an influence of the edge effect from a pixel that is two pixels or more away from the target pixel.

Embodiment 2. FIG.

  In the image forming apparatus according to the second embodiment of the present invention, the filter unit 41 calculates the filter output value with a peripheral pixel pattern different from the peripheral pixel pattern (FIG. 3) used for the filter calculation in the first embodiment.

  FIG. 6 is a diagram illustrating a specific example of the filter unit in the second embodiment. In the first embodiment, as shown in FIG. 3, the peripheral pixels used for the filter calculation are arranged in an oblique direction, but in the second embodiment, as shown in FIG. 6, they are used for the filter calculation. The peripheral pixels are arranged along the main scanning direction or the sub scanning direction.

  Since the other configuration and operation of the image forming apparatus according to the second embodiment of the present invention are the same as those of the first embodiment, the description thereof is omitted.

Embodiment 3 FIG.

  In the first and second embodiments of the present invention, the filter unit 41 uses a Laplacian filter that is a second-order differential filter. However, in the image forming apparatus according to the third embodiment of the present invention, the filter unit 41 includes 1 Compute basic data values using a second derivative filter.

  Note that other configurations and operations of the image forming apparatus according to the third embodiment of the present invention are the same as those in the first and second embodiments, and thus description thereof is omitted.

  Each embodiment described above is a preferred example of the present invention, but the present invention is not limited to these, and various modifications and changes can be made without departing from the scope of the present invention. It is.

  For example, in each of the above-described embodiments, the present invention is applied to a color image forming apparatus. However, it is of course possible to apply the present invention to a monochrome image forming apparatus.

  Further, in each of the above embodiments, the filter unit 41 may derive the basic data value using a peripheral pixel pattern including the peripheral pixels shown in FIG. 3 and the peripheral pixels shown in FIG. In that case, the above-described S1 to S3 may be derived by setting the filter coefficient of the target pixel to 8 and the filter coefficient of the peripheral pixels to -1.

  In each of the above embodiments, the filter unit 41 calculates the basic data value from the pixel values of one line of pixels in the main scanning direction (pixels C3 to C1, X, B1 to B3 in FIG. 6A). You may make it do. In this case, the filter unit 41 does not need to have a plurality of line buffers for holding a plurality of lines, and the circuit scale is reduced.

  The present invention is applicable to, for example, an electrophotographic image forming apparatus.

41 Filter unit 42 Toner amount calculation unit (an example of toner amount deriving unit)

Claims (6)

A filter unit capable of detecting edges in image data;
A toner amount deriving unit for deriving a toner consumption amount based on a basic data value obtained by adding the filter output value of the filter unit to the pixel value of the target pixel;
With
The filter unit calculates the filter output value from pixel values of pixels around the target pixel that fall within a window of a predetermined size,
The window includes a range of a maximum distance that gives an edge effect to the target pixel from the target pixel;
An image forming apparatus. The filter unit includes a plurality of filters for pixel values of peripheral pixels at a distance from the target pixel to a maximum distance that gives an edge effect to the target pixel from a distance of 1 from the target pixel. Calculate the output value
The toner amount deriving unit derives a toner consumption amount based on a basic data value obtained by adding the plurality of filter output values calculated for each distance by the filter unit to a pixel value of the target pixel. ,
The image forming apparatus according to claim 1.   The toner amount deriving unit performs a first calculation result by the filter unit on a pixel value of a peripheral pixel whose distance from the target pixel is (n−1) pixels, and a peripheral whose distance from the target pixel is n pixels Based on the second calculation result by the filter unit with respect to the pixel value of the pixel and the third calculation result by the filter unit with respect to the pixel value of the surrounding pixel whose distance from the target pixel is (n + 1) pixels, When the value of the second calculation result is lower than both the value of the first calculation result and the value of the third calculation result, the basic data is not added to the pixel value of the target pixel without adding the second calculation result. The image forming apparatus according to claim 2, wherein a value is derived.   The toner amount deriving unit may use the pixel value of the target pixel as the basic data value when the pixel values of all peripheral pixels whose distance from the target pixel is one pixel are zero. The image forming apparatus according to any one of claims 1 to 3.   The image forming apparatus according to claim 1, wherein the filter unit is a Laplacian filter. Calculating a filter output value for a peripheral pixel of a pixel value of a target pixel with a filter capable of detecting an edge in image data;
Deriving toner consumption based on a basic data value obtained by adding the filter output value to the pixel value of the pixel of interest,
In the filter, the filter output value is calculated from pixel values of pixels around the target pixel that fall within a window of a predetermined size,
The window includes a range of a maximum distance that gives an edge effect to the target pixel from the target pixel;
A toner amount calculation method characterized by the above.