JP2011137938A - Recording material discrimination apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly extract a feature quantity of a recording material and to perform more accurate recording material discrimination. <P>SOLUTION: A recording material discrimination apparatus is provided with: an orthogonal transform circuit 508 transforming an image read by an image reading sensor 123 into data of a two-dimensional space frequency region; an arithmetic circuit 505 calculating an amplitude spectrum from the data of the space frequency region transformed by the orthogonal transform circuit 508 and extracting the feature quantity of the recording material 1114 based on a distribution of the calculated amplitude spectrum; and a CPU 501 discriminates a kind of the recording material 1114, based on the feature quantity extracted by the arithmetic circuit 505. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a detection device that detects the surface smoothness of a recording material, and an image forming apparatus such as an ink jet printer, a copying machine, and a laser printer that controls image conditions based on the detection result of the surface smoothness of the recording material.

  An image forming apparatus such as a copying machine or a laser printer carries a latent image on a latent image carrier and visualizes the latent image as a developer image by applying a developer to the latent image carrier by a developing device. The developer image is transferred to a recording material conveyed in a predetermined direction by a transfer unit, and the recording material on which the developer image has been transferred by the transfer unit is heated and pressed under a predetermined fixing processing condition by a fixing device. Fix the agent image on the recording material. Conventionally, in such an image forming apparatus, for example, the size and type (hereinafter also referred to as paper type) of a recording material are set by a user on an operation panel or the like provided in the main body of the image forming apparatus. Then, in accordance with the setting, control is performed to change development conditions, transfer conditions, fixing processing conditions (for example, fixing temperature and conveyance speed of the recording material passing through the fixing device) or image processing. Further, for example, when the user sets the paper type at the time of printing from the host computer, the image forming apparatus performs control to change the development condition, the transfer condition, the fixing processing condition, or the image processing according to the designated paper type.

  Patent Document 1 proposes the following configuration. The surface image of the recording material is imaged by a CMOS sensor, and the maximum density pixel Dmax, the minimum density pixel Dmin of the surface image, and the contrast which is the difference between Dmax and Dmin are derived. (Surface fiber state) is determined. The recording material used for image formation includes multiple types of recording materials, such as plain paper, glossy paper whose surface fibers are compressed than plain paper, and rough paper whose surface fibers are not compressed than plain paper There is. The image forming apparatus variably controls development conditions, transfer conditions, or fixing conditions according to the type of the recording material, and forms an image so that an appropriate image according to the type of the recording material is obtained.

JP 2002-182518 A

  The recording material discrimination in the conventional image forming apparatus is a method for determining the recording material by calculating the surface smoothness from the contrast difference between the pixels of the captured image of the recording material, and the detection and discrimination method is simple, Accuracy that can be discriminated for plain paper, glossy paper, and rough paper is obtained. However, there are many kinds of recording materials used for image formation, and their surface smoothness is also various. For example, there are multiple types of rough paper, and there are differences in the surface smoothness of each. The conventional recording material discrimination method has a limit in discriminating such a slight difference in surface smoothness.

  The present invention has been made under such circumstances, and an object of the present invention is to accurately extract the characteristic amount of a recording material and to perform recording material discrimination with higher accuracy.

  In order to solve the above problems, the present invention comprises the following arrangement.

  (1) A recording material discriminating apparatus comprising a reading means for reading an image on the surface of a recording material, the converting means for converting the image read by the reading means into two-dimensional spatial frequency domain data, and the converting means An amplitude spectrum is calculated from the data of the spatial frequency domain converted by the above, and an extraction unit that extracts a feature amount of the recording material based on the calculated distribution of the amplitude spectrum, and the feature amount extracted by the extraction unit And a discriminating means for discriminating the type of the recording material based on the recording material.

  (2) An exposure unit that forms an electrostatic latent image on the image carrier, a developing unit that develops the electrostatic latent image to form a developer image, and a recording material conveyed at a predetermined conveyance speed. The recording material according to (1), wherein the recording material includes a transfer unit that transfers the developer image and a fixing unit that fixes the transferred developer image, and determines the type of the recording material. And a control unit that controls the exposure unit, the developing unit, the transfer unit, the fixing unit, or the conveyance speed based on the type of the recording material determined by the recording material determination unit. An image forming apparatus.

  According to the present invention, it is possible to accurately extract a feature amount of a recording material, and to perform recording material discrimination with higher accuracy.

FIG. 2 is a schematic configuration cross-sectional view of the image reading sensor according to the first embodiment and a diagram illustrating an output of the image reading sensor. Relationship diagram between transmitted light amount and basis weight of Example 1 Block diagram of recording material discriminating apparatus of Examples 1-3 Circuit block diagram of CMOS area sensor of Embodiment 1 FIG. 6 is a diagram for explaining extraction of a characteristic amount of a recording material according to the first embodiment. The figure explaining the area | region which divided | segmented the spatial frequency area | region of Example 1 into plurality. The graph explaining the relationship between the spatial frequency calculation result of Example 1 and a reference value Flowchart for explaining a recording material discrimination process according to the first embodiment. 1 is a diagram illustrating a configuration of an image forming apparatus according to first to third embodiments. FIG. 10 is a diagram for explaining extraction of a characteristic amount of a recording material according to the second embodiment. Flowchart for explaining a paper eye discrimination process and an image forming condition setting process according to the second embodiment. FIG. 6 is a diagram illustrating contrast detection according to the third embodiment.

  The mode for carrying out the present invention will be described in detail below with reference to examples.

[Configuration of recording material discrimination device]
FIG. 1A is a schematic cross-sectional view showing a schematic configuration of a recording material discriminating apparatus that performs surface smoothness of a recording material and detection of a reflected light amount or a transmitted light amount. The image reading sensor 123 includes a reflective LED 1111 serving as a first light irradiating unit, and a transmitting LED 1112 serving as a second light irradiating unit for detecting a transmitted light amount installed on the opposite side of the recording material 1114. Further, the image reading sensor 123 includes a sensor 1110 such as a CMOS area sensor serving as a reading unit. However, the sensor 1110 is not limited to the CMOS area sensor, and may be a CCD sensor or a photodiode sensor. A lens 1113 as an imaging lens is provided. Light that uses the LED 1111 for reflection as a light source is applied to the surface of the recording material 1114. The reflected light from the recording material 1114 is collected through the lens 1113 and imaged on the sensor 1110. As a result, the image reading sensor 123 reads the image on the surface of the recording material 1114. In this embodiment, the reflecting LED 1111 is arranged so that the LED light irradiates the recording material 1114 surface obliquely at a predetermined angle as shown in FIG.

[Output of image reading sensor and digital processing]
FIG. 1B is a diagram showing the relationship between the surface of the recording material 1114 read by the sensor 1110 of the video reading sensor 123 and an example in which the output of image data from the sensor 1110 is digitally processed to 8 × 8 pixels. The digital processing is performed by converting the analog output from the sensor 1110 into 8-bit pixel data by A / D conversion (not shown) as conversion means. Reference numeral 40 denotes an enlarged image of the surface of the recording material A of rough paper, which is relatively rough in the surface property of the recording material and in which irregularities due to the fibers of the recording material can be easily identified. 41 is an enlarged image of the surface of the recording material B of plain paper that is normally used in a general office, and 42 is a record of glossy paper (hereinafter referred to as gloss paper) in which the paper fibers are sufficiently compressed. It is a surface expansion picture of material C. These images 40 to 42 read by the sensor 1110 are digitally processed into images 43 to 45 shown in FIG. Thus, the image on the surface varies depending on the type of recording material. This is a phenomenon that occurs mainly because the fiber state on the paper surface is different. At this time, the reflected light amount of the recording material is detected from the total or average value of the light input to each pixel. The amount of reflected light of the recording material mainly depends on the whiteness of the surface of the recording material and varies depending on the type of recording material. The surface state of the paper fiber of the recording material can be identified from the digital image processed by reading the surface of the recording material by the sensor 1110. In addition to this, the amount of reflected light is also calculated, so that the recording material can be more accurately identified. It becomes possible.

  A method for measuring the transmittance of the recording material 1114 will be described. The light having the transmission LED 1112 as a light source irradiates the reading area of the image reading sensor 123 on the recording material from the opposite side of the image reading sensor 123 to the recording material 1114. FIG. 1C shows the relationship between the surface of the recording material 1114 read by the sensor 1110 of the video reading sensor 123 and the example in which the output from the sensor 1110 is digitally processed to 8 × 8 pixels using the transmissive LED 1112. FIG. Light transmitted through the recording material 1114 is collected through the lens 1113 and irradiated to the sensor 1110. At this time, the amount of transmitted light is determined from the total value or average value of light input to the entire area of the sensor 1110 or each pixel in a predetermined range. At this time, only one result among the plurality of light receiving pixels may be used.

[Relationship between basic weight and transmitted light amount]
FIG. 2 shows the relationship between the basis weight and the amount of transmitted light. For example, a recording material having a large basis weight such as thick paper has a small amount of transmitted light, but a recording material having a small basis weight such as thin paper has a large amount of transmitted light. This is a phenomenon that occurs mainly because the fiber state on the paper surface and the compressed state of the paper fiber are different.

[Sensor control circuit]
A control circuit block diagram of the sensor 1110 will be described with reference to FIG. When the CPU 501 serving as the determination unit gives an operation instruction of the sensor 1110 to the control register 507, the sensor 1110 starts imaging the recording material surface image. That is, charge accumulation in the sensor 1110 is started. When the sensor 1110 is selected by the Sl_select signal from the interface circuit 504 and the SYSCLK signal is generated at a predetermined timing, the imaged digital video data is transmitted from the sensor 1110 via the Sl_out signal. The imaging data received via the interface circuit 504 is calculated based on a calculation method described later in the orthogonal transformation circuit 508 and the calculation circuit 505 of the control circuit 502. The calculation result is set in, for example, the register A 506 among the registers A to D 506 for setting the calculation result of the recording material as a spatial frequency on the surface of the recording material. The CPU 501 determines the surface smoothness of the recording material from the value of the register A 506. Since the CPU 501 described above needs to process video sampling processing, gain and filter calculation processing from the sensor 1110 in real time, it is desirable to use a digital signal processor.

[Sensor circuit]
FIG. 4 is a circuit block diagram of the sensor 1110. When the S1_select signal 613 is activated, for example, the CMOS sensor unit 601 in which sensors for 8 × 8 pixels are arranged in an area starts to accumulate charges based on the received light. Next, when SYSCLK (system clock) 606 is applied, the vertical shift registers 602 and 603 sequentially select the pixel columns to be read out by the timing generator 607 and sequentially set the data in the output buffer 604. The data set in the output buffer 604 is transferred to the A / D converter 608 by the horizontal shift register 605. The pixel data digitally converted by the A / D converter 608 is controlled by the output interface circuit 609 at a predetermined timing, and is output to the Sl_out signal 610 while the Sl_select signal 613 is active. On the other hand, the A / D conversion gain of the A / D converter 608 can be variably controlled by the control circuit 611 from the Sl_in signal 612. For example, if the contrast of the captured image cannot be obtained, the CPU 501 can increase the contrast by increasing the A / D conversion gain of the A / D converter 608 and always capture with the best contrast.

[Spatial frequency calculation method]
A method for calculating the spatial frequency on the surface of the recording material will be described with reference to FIG. Images 70 to 72 are digitally processed images of the surface of the recording material. The recording material A 70 is an enlarged image of the surface of rough paper that is relatively rough in the surface properties of the recording material and that allows easy recognition of irregularities and paper grain due to the fibers of the recording material. The recording material B 71 is an enlarged image of the surface of plain paper normally used in a general office, and the recording material C 72 is an enlarged image of the surface of gloss paper in which the fibers of the paper are sufficiently compressed. The analog signal output from the sensor unit of the sensor 1110 is A / D converted to 8-bit pixel data, and is sent to the control circuit 502 as 8-bit data proportional to the brightness of the image. The pixel data sent to the orthogonal transformation circuit 508 via the interface circuit 504 is transformed into frequency components which are data in the spatial frequency domain by Expression (1-1) which is a discrete Fourier transform (73 to 75). ).

Here, N and M are the number of pixels in the vertical (y direction) and horizontal (x direction) of the sensor 1110, f (x, y) is the brightness of pixels in x columns and y rows, u is the spatial frequency in the x direction, v indicates a spatial frequency in the y direction. Further, the frequency component is obtained by decomposing pixel data for each frequency and indicating the magnitude of the amplitude as a spectrum, and is hereinafter referred to as an amplitude spectrum. This spectrum shows the characteristics of the original video.

In the arithmetic circuit 505, the amplitude spectrum for each spatial frequency is obtained by the equation (1-2).
Is calculated and set in the register A 506. Note that reference numerals 73 to 75 in FIG. 5 indicate distributions of amplitude spectra, and it can be seen that characteristic distributions corresponding to the respective recording materials 70 to 72 are shown.

[Two-dimensional amplitude spectrum]
Next, a two-dimensional amplitude spectrum will be described with reference to FIG. The image center represents the DC component in the x direction and the y direction. The image center in the y direction (A1 to A4 and G1 to G4 in FIG. 6) represents the DC component in the x direction. Similarly, the image center in the x direction (D1 to D4 and J1 to J4 in FIG. 6) represents the DC component in the y direction. The central portion of the image (A1 to L1 in FIG. 6) represents a low frequency component, and the peripheral portion of the image (A4 to L4 in FIG. 6) represents a high frequency component. Specifically, when recording paper A has many irregularities on the surface of the paper fibers, many shadows of fibers of various thicknesses are generated (FIG. 570). As a result, various shade widths are generated, and a large amplitude spectrum is generated up to the high frequency region (FIG. 576). On the other hand, on the surface such as the recording material C, the shadow of the fiber is small (FIG. 572). As a result, the change in shading is gentle, and the amplitude spectrum is concentrated in the DC region (FIG. 578). By this comparison, the paper type of the recording material is determined. Here, although discrete Fourier transform is used for the calculation of the amplitude spectrum, fast Fourier transform may be used with the number of pixels being 2 ⁿ , or may be converted into frequency components by other orthogonal transform.

[Extraction of recording material features and discrimination of recording material type]
A control flow by the CPU 501 serving as a printing condition control unit provided in the image forming apparatus 101 will be described. The arithmetic circuit 505 divides the spatial frequency for each region. In addition, three sets of areas are defined.
DC region 801 (A1-A4, D1-D4, G1-G4 and J1-J4 in FIG. 6)
Low frequency region 802 (A2 to L2 in FIG. 6)
High frequency region 803 (A3 to L3 in FIG. 6)

  The total number of frequencies whose amplitude spectrum is greater than or equal to a certain value (predetermined value or more) is counted for each region and defined as spatial frequency calculation results F801 to F803 on the surface of the recording material. Further, 76 to 78 in FIG. 5 are obtained by superimposing those obtained by dividing the spatial frequency region shown in FIG. 6 into a plurality of regions so that the characteristic amount of the recording material can be understood. Note that the feature amount of this embodiment is extracted due to the type of recording material.

The CPU 501 acquires the spatial frequency calculation results F801 to F803 on the surface of the recording material calculated by the arithmetic circuit 505 from the register A 506, and determines the type of the recording material based on the reference values R1 to R3 as follows. Here, the reference values R1 to R3 are threshold values corresponding to the spatial frequency calculation results F801 to F803 (hereinafter simply referred to as F801 etc.).
a) F801 ≧ R1 discriminated as gloss film b) F803 ≧ R3 discriminated as rough paper c) F803 <R3 & F802 ≧ R2 discriminated as plain paper d) other discriminated as undefined

  FIG. 8 is a flowchart of the recording material determination process executed by the CPU 501. If the CPU 501 determines that F801 is equal to or greater than R1 in S101, it determines that the recording material is a gloss film in S107. If the CPU 501 determines that F801 is not equal to or greater than R1 in S101, it determines whether or not F803 is equal to or greater than R3 in S102. If the CPU 501 determines that F803 is equal to or greater than R3 in S102, the CPU 501 determines that the recording material is rough paper in S106. If the CPU 501 determines that F803 is not equal to or greater than R3 in S102, it determines whether or not F803 is less than R3 and F802 is equal to or greater than R2 in S103. If the CPU 501 determines in step S103 that F803 is less than R3 and F802 is equal to or greater than R2, in step S105, the CPU 501 determines that the recording material is plain paper. If the CPU 501 determines that F803 is less than R3 and F802 is not equal to or greater than R2 in S103, it determines that the recording material is undefined in S104.

[Relationship between reference value and spatial frequency calculation result]
Next, the relationship between the reference values R1 to R3 and the spatial frequency calculation results F801 to F803 will be described with reference to FIG. FIG. 7A shows the relationship between the reference value R 1 and the spatial frequency calculation result F 801 in the DC region 801. On a smooth surface such as the recording material C, the shadow of the fiber is small and the amplitude spectrum is concentrated in the DC region. Therefore, the spatial frequency calculation result F801 in the DC region of the recording material C exceeds the reference value R1. FIG. 7C shows the relationship between the reference value R 3 and the spatial frequency calculation result F 803 in the high frequency region 803. When there are many irregularities on the surface of the paper fiber as in the recording material A, many shadows of fibers of various thicknesses are generated, and a large amplitude spectrum is generated up to the high frequency region. Therefore, the spatial frequency calculation result F803 in the high frequency region of the recording material A exceeds the reference value R3. Finally, FIG. 7B shows the relationship between the reference value R 2 and the spatial frequency calculation result F 802 in the low frequency region 802. When the unevenness of the paper fiber on the surface is medium like the recording material B, the spatial frequency calculation result F802 in the low frequency region exceeds the reference value R2. However, the spatial frequency calculation result F803 in the high frequency region does not exceed the reference value R3. The recording material can be discriminated by the above combination. The above determination is not affected by the paper grain because the information in the x direction and the y direction is processed simultaneously. Therefore, a good discrimination result can be obtained for both longitudinal and lateral recording materials.

[Application to image forming equipment]
FIG. 9 shows a schematic configuration of the image forming apparatus described in the present embodiment. Here, a tandem color image forming apparatus is taken as an example. The image forming apparatus 101 includes an image forming unit that is an image forming unit for four colors of yellow (Y), magenta (M), cyan (C), and black (Bk). Each image forming unit includes exposure devices 118 to 121 that are exposure units that form an electrostatic latent image on the image carrier, photosensitive drums 106 to 109 that are image carriers, and transfer rollers 110 to 113 that are transfer units. . The photosensitive drums 106 to 109 are included in removable cartridges 114 to 117. The recording material fed by the pickup roller 103 from the paper feed cassette 102 is discriminated by the video reading sensor 123 which is a video reading device. The image on the surface of the recording material read by the image reading sensor 123 is digitally processed and converted into a spatial frequency component by the orthogonal transformation circuit 508 described with reference to FIG. 3, and the characteristic amount of the recording material is extracted by the arithmetic circuit 505. Is done. The CPU 501 determines the recording material from the characteristic amount of the recording material, and performs image processing, development bias, temperature control value of the fixing unit, or recording material conveyance speed according to various characteristics such as the surface property of the recording material and the thickness of the recording material An optimal image can be obtained by variably controlling. The recording material is conveyed to a nip portion between the photosensitive drums 106 to 109 and the transfer rollers 110 to 113 by a conveying belt 105 that is rotationally driven by a driving motor 104, and a developer image is sequentially superimposed and transferred at each color image forming portion. A color image is formed on the recording material. The recording material is heated and fixed by the fixing device 122 and conveyed outside the image forming apparatus.

  Next, a method performed by the CPU 501 for setting optimal image forming conditions for the determined recording material will be described. Examples of the control of various image forming conditions executed by the CPU 501 include the following. For example, when the type of the recording material is glossy paper, the CPU 501 performs control to change the color by changing the γ curve for plain paper during image processing. This is because when printing is performed using gloss paper, it is desired to increase the contrast on the recording material. Further, the CPU 501 determines the type of the fed recording material, and controls to change the recording material conveyance speed in accordance with the result. Specifically, when the surface of the recording material is rough paper, which is rougher than plain paper, the contact with the fixing film on the surface of the recording material is low, and heat transfer to the recording material is uneven at the fixing nip. The amount of heat necessary for melting the toner is not sufficiently transmitted to the recording material side. For this reason, the rough paper has a problem that the heat amount is insufficient and the fixing property is lowered. Therefore, when the CPU 501 determines that the type of the recording material is rough paper, the recording material conveyance speed is set so that the amount of heat supplied to the rough paper per unit time increases. Set slower than the transport speed. Further, in the case of an OHT or a gloss film, it is possible to improve the image quality by discriminating these and improving the fixability of the toner adhering to the surface of the recording material and increasing the gloss. If the determination result is undefined, the CPU 501 performs control under a fixing condition such that the conveyance speed and the fixing temperature are considered to cause the least damage to the image forming apparatus main body.

  As described above, this embodiment is characterized in that the recording material is discriminated by converting the image on the surface of the recording material into a frequency component and calculating the spatial frequency calculation result. According to the present embodiment, the two-dimensional spectrum can easily remove the effect of the paper grain, and the frequency component can easily extract the characteristics of the fibers constituting the recording material, which is highly discriminating. Accuracy can be obtained. In addition, a favorable image can be obtained by performing an image forming process by an optimum electrophotographic process under various conditions.

[Paper detection processing]
In the second embodiment, details of the paper grain discrimination by extracting the characteristic amount of the recording material using the two-dimensional frequency component will be described. Since the basic configuration other than the signal processing method for the recording material surface image is the same as that of the first embodiment, detailed description thereof will be omitted, and description will be made using the same reference numerals. Note that the feature amount of this embodiment is extracted due to the grain of the recording material. FIG. 10 is a diagram for explaining the details of the paper grain discrimination using the two-dimensional frequency component. The orthogonal transform circuit 508 converts the pixel data of the recording material D 1003 and the recording material E 1005 into frequency components (1004 and 1006). Here, the recording material D is a vertical recording material, and the recording material E is a paperless recording material. The longitudinal recording material D generates a strong high frequency spectrum in the x direction due to the effect of the paper pattern, but does not generate a high frequency spectrum in the y direction (1004). On the other hand, on the surface such as the recording material E having no paper, the amplitude spectrum is concentrated in the DC region (1006).

First, the arithmetic circuit 505 divides the spatial frequency, which is calculated in the same manner as in the first embodiment, for each region. In addition, two sets of areas are defined.
Horizontal region (1001) (C1 to C4, E1 to E4, I1 to I4 and K1 to K4 in FIG. 6)
Longitudinal area (1002) (B1 to B4, F1 to F4, H1 to H4 and L1 to L4 in FIG. 6)

  The arithmetic circuit 505 counts the total number of frequencies having an amplitude spectrum equal to or larger than a certain value for each region, defines them as the paper grain calculation results F1001 and F1002 on the surface of the recording material, and stores them in the register B 506, for example.

The CPU 501 obtains the paper grain calculation results F1001 to F1002 on the surface of the recording material calculated by the arithmetic circuit 505 from the register B 506, and determines the paper texture of the recording material. In order to discriminate the recording paper, the difference between the paper grain calculation result F1001 of the horizontal eye area 1001 and the paper grain calculation result F1002 of the vertical eye area 1002 is obtained, and based on the difference and the reference value R4 or R5, To determine. The reference values R4 and R5 are threshold values corresponding to the paper grain calculation results F1001 and F1002.
e) F1001-F1002 ≧ R4 discriminated from horizontal eye f) F1002-F1001 ≧ R5 discriminated from vertical eye g) Other

  FIG. 11A shows a flowchart of the recording material discrimination process executed by the CPU 501. In S201, the CPU 501 determines whether the difference between F1001 and F1002 is R4 or more. If the CPU 501 determines in S201 that the difference between F1001 and F1002 is equal to or greater than R4, it determines that the recording material is horizontal in S205. If the CPU 501 determines in S201 that the difference between F1001 and F1002 is not equal to or greater than R4, in S202, the CPU 501 determines whether or not the difference between F1002 and F1001 is equal to or greater than R5. If the CPU 501 determines in S202 that the difference between F1002 and F1001 is equal to or greater than R5, it determines that the recording material is a vertical eye in S204. If the CPU 501 determines in S202 that the difference between F1002 and F1001 is not equal to or greater than R5, in S203, the CPU 501 determines that the recording material has no paper.

[Setting image forming conditions suitable for paper texture]
An image forming condition setting method that is optimal for the grain of the recording material determined by the CPU 501 will be described with reference to FIG. When the determined recording material has a horizontal grain (S1401), the CPU 501 performs control to lower the conveyance speed and the fixing temperature than usual (S1405). This is because when printing is performed using a recording material having a paper pattern, moisture contained in the recording material is evaporated by being heated to a high temperature by the fixing device 122, and the recording material is curled along the paper texture. In the case of a horizontal recording material, curling occurs at right angles to the transport direction, which causes a paper jam. By reducing the conveyance speed and the fixing temperature, the curl amount can be reduced and the occurrence of paper jam can be suppressed. When the determined recording material has a vertical grain (S1402), the CPU 501 controls the conveyance speed and the fixing temperature as usual (S1404). This is because, in the case of a longitudinal recording material, curling occurs in the transport direction, and the occurrence probability of paper jam is low. If the CPU 501 determines that the paper of the determined recording material is neither horizontal nor vertical and has no paper, the CPU 501 controls the conveyance speed and the fixing temperature as usual (S1403). This is because the probability of curling is low in the case of a recording material having no paper. Further, when the paper pattern determined to be different from the recommended paper pattern for the image forming apparatus is different, the CPU 501 can display a warning on the display panel, which is a display unit, and allow the user to change the paper conveyance direction.

  As described above, this embodiment is characterized in that the recording material surface image is converted into a frequency component, and the paper grain judgment of the recording material is performed by calculating the paper grain calculation result. According to the present embodiment, the feature amount of the recording material can be accurately extracted, and the paper grain discrimination with high accuracy can be performed. Further, even under various conditions, it is possible to obtain a good image by performing an optimal electrophotographic process. In addition, an appropriate electrophotographic process can be selected from the paper eye discrimination result, and the conveyance reliability and discharge stackability of the recording material can be improved.

  Since the basic configuration of the third embodiment is the same as that of the first embodiment except for the signal processing method for the recording material surface image, detailed description thereof is omitted. As proposed in Japanese Patent Application Laid-Open No. H10-228867, conventional recording material type discrimination is performed by processing a continuous signal output from an image reading apparatus. Specifically, the surface image of the recording material is acquired in a line shape, the surface smoothness of the recording material is determined based on the contrast between the maximum luminance pixel and the minimum luminance pixel in the one line, and the type of the recording material is determined. When the paper fiber on the surface is rough like the recording material A in FIG. 1B, many shadows of the fiber are generated. As a result, the difference between the bright part and the dark part becomes large, and the contrast becomes large. On the other hand, on the surface such as the recording material C in FIG. 1B, the shadow of the fiber is small and the contrast is small. This comparison determines the paper type of the recording material.

[Contrast detection of recording material surface]
The details of the method for detecting the contrast of the surface of the recording material will be described with reference to FIG. In FIG. 12, an image 130 is an image obtained by digitally processing the image of the surface of the recording material. Analog data output from the sensor unit of the sensor 1110 is A / D converted to 8-bit pixel data, and 8-bit data is determined in proportion to the brightness of the image. At that time, the maximum contrast 131 is the darkest part in the first line of 8 × 8 pixels. In the example shown in the figure, “80” h, and the minimum contrast 132 is in the first line of 8 × 8 pixels. Is the brightest part, and is “10” h in the example of the figure. At this time, the difference between the two values is '80'h-'10'h ='70'h. That is, the difference between the maximum contrast value and the minimum value in the first line is “70” h. Similarly, the maximum contrast 133 is the value of the second line and is the darkest part '80'h, the minimum contrast 134 is the value of the second line and the brightest part'20'h, and the difference is'80'h-'20'h = '60'h. The maximum contrast 135 is the value of the eighth line and is the darkest part '80'h, the minimum contrast 136 is the value of the eighth line and the brightest part'10'h, and the difference is'80'h-'10'h = '70'h. The value obtained by adding the difference between the maximum and minimum values for each line in the horizontal direction for all lines is defined as the contrast calculation result value on the surface of the recording material, and the surface smoothness of the recording material is determined based on this magnitude. The paper type can be discriminated.

  However, as described above, some recording materials have grain. For this reason, the image reading device may be installed obliquely with respect to the recording material so that the same discrimination performance can be obtained regardless of whether the image is vertical or horizontal. However, for discriminating the recording material, it is also important to detect the thickness of the fibers constituting the recording material, and the performance of discriminating the thickness of the fibers decreases when the image reading device is installed obliquely. there is a possibility. Therefore, the recording material discriminating apparatus described in the present embodiment is characterized in that the direction in which the surface image of the recording material is acquired in a line shape is changed depending on the paper pattern. Specifically, when the paper grain discrimination result described in the second embodiment is a vertical grain, the discrimination is performed horizontally (x direction in FIG. 12). Similarly, if the paper eye discrimination result is a horizontal eye, the discrimination is performed vertically (y direction in FIG. 12). That is, in order to discriminate the paper pattern, the feature amount of the recording material described in the second embodiment is extracted. By the above operation, it becomes possible to always perform the calculation perpendicular to the fiber (to the paper grain), and stable recording material discrimination can be performed regardless of the paper grain of the recording material. Here, although the contrast of the luminance pixel of the pixel is used as the recording material discrimination method, the effect of the present embodiment is not limited to this discrimination method, and can be applied to all discrimination methods for discrimination in a line shape. .

  As described above, the present embodiment is characterized in that the recording material discrimination method is changed according to the paper grain discrimination result to improve the discrimination performance of the recording material. According to the present embodiment, the characteristic amount of the recording material can be accurately extracted, and stable recording material discrimination can be performed regardless of the grain of the recording material. Further, even under various conditions, it is possible to obtain a good image by performing an optimal electrophotographic process.

123 Image Reading Sensor 501 Judgment Unit (CPU)
502 control circuit 505 arithmetic circuit 508 orthogonal transform circuit

Claims (6)

A recording material discriminating device comprising a reading means for reading an image of the surface of a recording material,
Conversion means for converting the video read by the reading means into two-dimensional spatial frequency domain data;
An extraction means for calculating an amplitude spectrum from the data of the spatial frequency domain converted by the conversion means, and extracting a characteristic amount of the recording material based on the distribution of the calculated amplitude spectrum;
Discriminating means for discriminating the type of the recording material based on the feature amount extracted by the extracting means;
A recording material discriminating apparatus comprising:   The extraction unit divides the spatial frequency region into a plurality of regions, and extracts the feature amount of the recording material by counting the amplitude spectrum that is a predetermined value or more for each of the divided regions. Item 4. The recording material discrimination device according to Item 1.   The recording material determination apparatus according to claim 1, wherein the determination unit determines a paper pattern of the recording material based on the feature amount extracted by the extraction unit.   The discriminating unit calculates a contrast of an image read by the reading unit along a direction perpendicular to the discriminated paper grain, and discriminates the type of the recording material based on the calculated contrast. Item 4. The recording material discrimination device according to Item 3. An exposure unit that forms an electrostatic latent image on an image carrier; a developing unit that develops the electrostatic latent image to form a developer image; and the developer on a recording material conveyed at a predetermined conveyance speed. An image forming apparatus comprising: transfer means for transferring an image; and fixing means for fixing the transferred developer image,
The recording material discrimination device according to any one of claims 1 to 4, wherein the type of the recording material is discriminated.
An image forming apparatus comprising: the exposure unit, the developing unit, the transfer unit, the fixing unit, or a control unit that controls the conveyance speed based on the type of the recording material determined by the recording material determination device. apparatus. An exposure unit that forms an electrostatic latent image on an image carrier; a developing unit that develops the electrostatic latent image to form a developer image; and the developer on a recording material conveyed at a predetermined conveyance speed. An image forming apparatus comprising: transfer means for transferring an image; and fixing means for fixing the transferred developer image,
The recording material discriminating apparatus according to claim 3, wherein the recording material discriminating paper is discriminated.
An image forming apparatus comprising: the fixing unit and a control unit that controls the conveyance speed according to the grain of the recording material determined by the recording material determination device.