JP2012220405A - Conveyance amount measuring apparatus and recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an accurate moving amount of a moving amount measuring pattern on a recording paper sheet by accurately picking up a pattern suitable for pattern matching without increasing a data processing amount.SOLUTION: A conveyance amount measuring apparatus comprises conveyance means which conveys a recording medium in a predetermined conveyance direction, and is configured to measure the conveyance amount of the recording medium in a recording device which records an image on the recording medium to be conveyed by using a recording head. The conveyance amount measuring apparatus comprises an image sensor 101-1 and an image sensor 101-2. The image sensor 101-1 has an imaging area of a predetermined range for the recording medium to be conveyed, and acquires image data for extracting a moving amount measuring pattern and calculating a moving amount of the moving amount measuring pattern for measuring the conveyance amount of the recording medium. The second image sensor 101-2 has an imaging area of a predetermined range disposed at an upstream side of the image sensor 101-1 in the conveyance direction and acquires image data, having a lower resolution than that of the image sensor 101-1, for selecting the range to extract the moving amount measuring pattern.

Description

  The present invention relates to a conveyance amount measuring apparatus that reads a predetermined area on the surface of a recording sheet using a two-dimensional image sensor and measures a conveyance amount by a recording sheet conveyance unit from movement information of a read image.

  For example, in a recording apparatus that records an image on the surface of a recording sheet while conveying the recording sheet in a predetermined direction, such as an inkjet printer, the conveyance accuracy of the recording sheet during printing greatly affects the quality of the printed image. In Patent Document 1, in order to accurately convey a recording sheet, the amount of rotation of a roller or the like that conveys the recording sheet is not detected, but the amount of movement of the conveyed recording sheet is directly detected. A configuration that eliminates an error from the amount of movement of the system is disclosed.

JP 2007-217176 A

  By the way, the technique disclosed in Japanese Patent Laid-Open No. 2004-228620 has both resolution of specifying a pattern suitable for measuring the conveyance amount of the recording paper and detecting the conveyance amount of the recording medium by pattern matching of this pattern. This is done using a certain sensor. A high resolution image is required to perform pattern matching with high accuracy. For this reason, there is a problem that the amount of data processing for measuring the conveyance amount of the recording paper is large.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is capable of specifying a pattern for measuring the conveyance amount of a recording sheet and measuring the conveyance amount of the recording sheet by pattern matching with a small data processing amount. It is an object of the present invention to provide an apparatus and a recording apparatus including the apparatus.

  The transport amount measuring apparatus of the present invention includes transport means for transporting a recording medium in a predetermined transport direction, and measures the transport amount of the recording medium in a recording apparatus that records an image on the transported recording medium using a recording head. A conveyance amount measuring device that has an imaging area in a predetermined range with respect to a recording medium to be conveyed, and extracts a movement amount measurement pattern for measuring the conveyance amount of the recording medium and moves the movement amount measurement pattern. A first imaging unit that obtains image data for calculating the amount; and an imaging region of a predetermined range that is disposed upstream of the first imaging unit in the transport direction, the first imaging unit And a second imaging means for acquiring image data having a lower resolution than the first imaging means for selecting a range from which the movement amount measurement pattern is extracted. And

  According to the present invention, the first imaging unit is selected by selecting a range for extracting the movement amount measurement pattern in the first imaging unit based on the image data obtained from the second imaging unit having a low resolution. It is possible to reduce the amount of data processing required for extracting the movement amount measurement pattern using the image data obtained from the above and calculating the movement amount.

1 is a schematic configuration diagram of a recording apparatus to which the present invention is applied. It is a figure which shows the structural example of an imaging device. It is a figure which shows an example of a structure of the image sensor used for an imaging device. It is a conceptual diagram of the arrangement configuration and pattern recognition of image sensors having different resolutions used in the present invention. It is a circuit block diagram of the image sensor of this invention. It is a flowchart explaining the conveyance amount measurement operation | movement which concerns on one Embodiment of this invention. It is a flowchart which shows an example of the position acquisition process of the target pattern from the image data obtained from a high resolution image sensor. It is a flowchart which shows an example of the target pattern extraction process from the image data obtained from a low-resolution image sensor.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a schematic view of an ink jet printer as a recording apparatus to which the present invention is applied. Although the present invention has been described using an ink jet printer, the present invention is not limited to this and can be applied to other types of recording apparatuses such as a laser.

  In FIG. 1, 100 is an imaging device, 103 is a recording sheet as a recording medium, 130 is a paper feed tray, 140 is a transport device, 150 is a paper feed roller, 160 is a paper discharge roller, 180 is a carriage, 182 is a print head, Reference numeral 200 denotes a controller.

  The controller 200 includes hardware such as a processor and a memory, and necessary software. The controller 200 processes image data from the imaging apparatus 100 and controls the entire recording apparatus such as the transport apparatus 140 and the recording head 182.

  In this ink jet printer, the recording paper 103 disposed on the paper feed tray 130 is supplied toward the recording head 182 by a rotating paper feed roller 150. The supplied recording paper 103 is sandwiched between the transport driving roller 142 and the transport driven roller 141 of the transport device 140, transported in the paper transport direction A, and set at the recording start position. The recording head 182 forms an image by ejecting ink onto a unit area of the recording paper 103 while being moved in a direction (main scanning direction) orthogonal to the paper conveyance direction A by the carriage 180. When the image formation in this unit area is completed, the recording paper 103 is conveyed by the conveying device 140 by a movement amount corresponding to the width of the unit area. By repeating the recording on the recording paper 103 and the conveyance of the recording paper 103, an image is recorded on the recording paper 103. When the recording of the image on the recording paper 103 is completed, the recording paper 103 is discharged by the paper discharge roller 160.

  As shown in FIGS. 1 and 2, the imaging apparatus 100 is disposed on the opposite side of the printing surface of the recording paper 103 so as to face the recording paper 103, and images the back surface of the recording paper 103. Note that the imaging apparatus 100 can be arranged on the printing surface side of the recording paper 103. The imaging apparatus 100 includes an LED 102 that is a light emitting unit and an image sensor 101. The LED 102 is, for example, a red LED having an emission wavelength of about 660 nm. The light from the LED 102 is reflected by the back surface of the recording paper 103 and enters the image sensor 101. Further, as shown in FIG. 3, the image sensor 101 has a low-resolution image sensor 101-2 as a first imaging unit on the upstream side and a second imaging unit on the downstream side in the paper conveyance direction. High-resolution image sensor 101-1. That is, the image sensor 101 includes two image sensors having different resolutions, and these are adjacent to each other in the paper transport direction. Each of the image sensors 101-1 and 101-2 has an imaging area within a predetermined range with respect to the recording paper 103 being conveyed.

  Here, the principle of the present invention will be described with reference to FIG. The low-resolution image sensor 101-2 has a distance of 40 μm between the image sensors, a pixel count of 256 × 128 dots, and a total pixel count of 32768 dots. That is, the size of the low resolution image sensor 101-2 is 10.24 mm × 5.12 mm. The high-resolution image sensor 101-1 has a distance of 10 μm between elements, a pixel count of 1024 × 256 dots, and a total pixel count of 262174 dots. The size of the high resolution image sensor 101-1 is 10.24 mm × 2.56 mm. The combined size of the image sensor 101 is 10.24 mm in the width direction of the recording paper and 7.68 mm in the recording paper conveyance direction, and the surface of the recording paper can be imaged within this range. .

  Of these two types of image sensors 101-1 and 101-2, the high-resolution image sensor 101-1 is a movement amount measurement pattern (hereinafter referred to as a target) used to calculate the movement amount (conveyance amount) of the recording paper. It is used to acquire image data for extracting (pattern). The target pattern is TP shown in FIG. The low-resolution image sensor 101-2 disposed on the upstream side in the conveyance direction of the recording paper 103 with respect to the image sensor 101-1, the image of the target pattern TP in the entire imaging region of the high-resolution image sensor 101-1. It is used to acquire image data for selecting a region used for extraction. Although the captured image of the surface of the recording paper 103 obtained from the low-resolution image sensor 101-2 is rough, even if data of all pixels is acquired, the total number of pixels is relatively small and a long processing time is required. do not do. All pixels of the low-resolution image sensor 101-2 are searched, and based on the contrast between the pixels, an area used for extracting the target pattern of the high-resolution image sensor 101-1 is selected. The target pattern TP is extracted from the image data of the selected region of the high-resolution image sensor 101-1, and the movement amount of the target pattern TP is calculated. The amount of movement of the target pattern TP is the amount of conveyance of the recording paper 103. That is, an area in which a target pattern suitable for use in measuring the actual movement amount by the high resolution image sensor 101-1 can be obtained is selected from all the pixels of the high resolution image sensor 101-1. . Thereby, the area of interest of the high-resolution image sensor 101-1 is limited to the selected area, and the amount of pixel data to be processed is reduced. By combining these two types of resolution image sensors 101-1 and 101-2, an image pattern suitable for pattern matching can be searched from a wide range of images, and the amount of processing data can be reduced.

  FIG. 5 is a diagram showing a circuit configuration of the image sensor 101. The number of pixels of the image sensor 101 is as described above. Here, for the sake of simplicity, the operation of the image sensor will be described as a 3 × 3 9-pixel image sensor as shown in FIG. In FIG. 5, reference numeral 110 denotes a timing generator that controls driving of each pixel arranged in a matrix. Reference numeral 111 denotes a horizontal shift register driven by the timing generator 111, and 112 denotes a vertical shift register. The horizontal shift register 111 outputs H0 to H2 as signal lines for driving each pixel, and the vertical shift register 112 outputs V0 to V2. Reference numeral 113 denotes a photodiode which is an image sensor. This is a photoelectric conversion element that converts the photodiode of each pixel into a voltage corresponding to the intensity of the incident light. Next, a driving method for each pixel will be described. After a certain imaging time has elapsed, a voltage corresponding to the captured image is generated in each pixel. First, the vertical shift register 112 generates a pulse on the signal line V0. With this pulse, the transistor connected to each photodiode is driven, and the voltage on the cathode side of the photodiode 113 is output to the terminal on the opposite side of the photodiode of the transistor. Here, three rows of data connected to the signal line V0 appear on the vertical signal line. Next, the signal lines H0 to H2 from the horizontal shift register 111 are sequentially driven. First, the transistor connected to the signal line is driven by the pulse output to H0, and the voltage of the phototransistor on the line H0 among the phototransistors in the first row appears in the input signal to the amplifier 204. Next, H1 is driven, the output of the adjacent phototransistor is input to the amplifier 204, and finally H2 is driven. By sequentially driving the horizontal shift register, data of three elements in the first row can be taken. Similarly, V1 is driven from the vertical shift register, and the outputs of the three phototransistors in the center column are output to the signal line. In this way, the data of all the pixels on the matrix can be captured by sequentially driving the horizontal shift register 111 and the vertical shift register 112. Here, the operation of capturing the imaging data of all the pixels of the 3 × 3 matrix has been described, but only the data of the desired pixel is captured by selectively driving the signal lines from the horizontal shift register 111 and the vertical shift register 112. Is possible. In the present invention, as described above, pixel data of the high-resolution image sensor 101-1 is selectively acquired in order to reduce the amount of data from the high-resolution image sensor 101-1. This is realized by selecting the drive signal from each shift register in this way.

  Next, the operation for measuring the conveyance amount of the recording paper according to the embodiment of the present invention will be described using the flowcharts shown in FIGS. 6 shows the processing procedure of the transport amount measurement operation, FIG. 7 shows the target pattern position acquisition processing from the image data obtained from the high resolution image sensor, and FIG. 8 shows the image data obtained from the low resolution image sensor. 2 shows an example of processing for extracting a target pattern from.

  In FIG. 6, it is first determined whether or not the search area for the target pattern in the high-resolution image sensor 101-1 selected based on the search result of the low-resolution image sensor 101-2 is set (step S501). ). The target pattern search area is an area selected according to the target pattern obtained from the low-resolution image sensor 101-2. Here, since this is the first operation, the process proceeds to step S504.

  In step S504, an area where a target pattern suitable for pattern matching can be obtained is selected from the image data obtained from the low-resolution image sensor 101-2. The operation of the low-resolution image sensor 101-2 will be described later with reference to the flowchart shown in FIG.

  Next, in step S505, a search area for acquiring a target pattern in the high-resolution image sensor 101-1 is calculated from the pixels selected by the low-resolution image sensor 101-2. The search start position in the high-resolution image sensor 101-1 is determined by the physical distance between both sensors and the amount of movement of the target pattern by one recording sheet conveyance.

  Next, in step S506, the recording paper is conveyed by the conveyance amount determined by the printing range of one scan with the recording head. If the printing operation for one page is not completed in step S507, the process returns to step S502.

  In step S502, the current position of the target pattern recognized by the high-resolution image sensor 101-1 is acquired, and the amount of movement of the target pattern is calculated. That is, the amount of movement of the target pattern due to the conveyance of the recording paper 103 is calculated.

  Next, in step S503, a target pattern used for calculation of the next transport amount is extracted by searching an area of the high-resolution image sensor 101-1 selected from the selection result of the low-resolution image sensor 101-2. (recognize.

  Next, in step S504, a search area for target pattern calculation in the next high resolution image sensor 101-1 is selected based on the image data obtained from the low resolution image sensor 101-2.

  Thus, the calculation of the movement amount of the previously extracted target pattern, the search of the search range of the previously selected target pattern to recognize the target pattern, and the new selection of the search range of the target pattern are performed once. This is executed for each recording paper transport operation.

  Next, an operation for selecting a target pattern search area in the high-resolution image sensor 101-2 based on image data obtained from the low-resolution image sensor 101-1 will be described with reference to the flowchart in FIG. In the low-resolution image sensor 101-2, the entire pixel range is searched and the position of a specified pixel is acquired. First, after specifying the start position in step S701, the image density of the pixel of interest is acquired in step S702. This density acquisition is performed by detecting the desired photodiode potential by driving the shift register of the image sensor 101 as described above. In step S706, the shift registers 111 and 112 are sequentially driven. If the acquisition of data for all the pixels is completed in step S703, the coordinates of the pixel having the maximum density among all the pixels are acquired in step S704.

  As shown in a dotted line X in FIG. 4, when the surface of the recording paper is imaged, the surface that is not the printing surface of the recording paper is imaged, so the image to be captured is basically white data. However, among these, a portion suitable for making a target pattern that is easy to perform pattern matching has a density that is relatively close to the black side. Therefore, a pixel having the maximum density is selected from all pixels. This reflection density depends on the material of the recording paper and the like. In order to make the density difference noticeable, it is necessary to adjust the light emission amount of the light emitting side LED. From the pixel coordinates determined in step S704 and the next scheduled recording paper conveyance amount, the position corresponding to the pixel coordinates on the high resolution side is calculated, which is the high resolution image sensor 101-1. The search position at. The position of the recording paper corresponding to the pixel coordinates determined in step S704 must be moved to the defense range of the high resolution sensor by the next recording paper conveyance. For this reason, in the case of a printer in which the recording paper conveyance amount at one time is variable depending on the printing mode or the like, it is necessary to determine the coordinates according to the conveyance amount.

  Next, the target pattern position acquisition operation in the high-resolution image sensor will be described with reference to FIG. First, as described above, designated search start coordinates are set from the detection result of the low-resolution image sensor in step S601.

  Next, in step S602, the density of the pixel at that coordinate is examined. The density acquisition method is the same as that for driving with a low-resolution sensor. Here, the sensor is partially driven according to the search range. If the density is higher than the specified value, the process proceeds to step S603, and the density of the peripheral pixels of the pixel is examined. On the contrary, if the density of the peripheral pixel of the target pixel is equal to or lower than the specified value, the target pixel is recognized as a feature point, and its coordinates are stored in the memory as a pixel for creating the target pattern in step S604. By repeating this, when the investigation of all the pixels in the designated search range is completed, the process proceeds to step S607. In step S607, it is checked whether the number of pixels picked up as feature points is four or more. If the number is three or less, the process proceeds to step S608, where the threshold value for determining the density is changed, and the feature point is selected again.

  In the case where four or more feature points are selected in step S607, as shown in FIG. 4, first, the image of the target pattern from the coordinates of one feature point A and the vectors to the other feature points B to D. Create In this way, the target pattern is created by the high resolution sensor, and the conveyance amount of the recording paper is measured from the movement amount of the target pattern. Also, for the confirmation of the target pattern movement destination, the movement destination is predicted from the conveyance amount of the recording paper. Therefore, the pattern image creation operation is performed in the same manner, and the pixel position where the pattern matches is calculated. Is calculated.

  According to the present embodiment, two types of image sensors having different resolutions are provided, and the pattern position that can be predicted to be suitable for movement amount measurement by the image sensor on the low resolution side is selected, so that the data processing amount is not increased. The range of the monitoring area can be expanded. As a result, it is possible to select a pattern that is more effective for recognition.

  In addition, in the high resolution image sensor, the target pattern selection is performed in a limited area selected in advance using the image data from the low resolution image sensor, so the data processing amount can be reduced here, too. In addition, it is possible to accurately measure the transport amount with high resolution.

  Further, according to the present embodiment, since it is not necessary to increase the size of the high-resolution image sensor, the circuit scale can be suppressed to be small, which is effective in terms of cost.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.
In the first embodiment, the search start position of the high-resolution image sensor is selected from the search result of the low-resolution image sensor. However, the destination of the target pattern determined by the high-resolution sensor after transporting the recording paper is confirmed. As a result, it is possible to measure the degree of movement in the direction (main scanning direction) orthogonal to the recording sheet conveyance direction, that is, the skew amount of the recording sheet conveyance. From this result, it is also possible to consider the amount of deviation in the direction perpendicular to the recording sheet conveyance direction to the search start position of the next determined high resolution image sensor. By minimizing the amount of deviation in the orthogonal direction, the search range of the high resolution sensor can be reduced.

  In the above embodiment, the recording apparatus that moves the recording head in the main scanning direction has been described as an example. However, the present invention is not limited to this, and is also applicable to a recording apparatus in which the recording head is fixed. Is possible.

  Although the case where two image sensors having different resolutions are used has been described in the above embodiment, the present invention is not limited to this, and image sensors having the same resolution may be used. In this case, the data processing amount is reduced by thinning out the used pixels of the image sensor that acquires low-resolution image data.

DESCRIPTION OF SYMBOLS 100 Imaging device 101 Image sensor 101-1 High-resolution image sensor (2nd imaging means)
101-2 Low-resolution image sensor (first imaging means)
102 LED light emitting unit 103 Recording paper

Claims (4)

A transport amount measuring device that includes a transport unit that transports a recording medium in a predetermined transport direction, and measures a transport amount of the recording medium in a recording apparatus that records an image on the transported recording medium using a recording head,
Extraction of movement amount measurement pattern for measuring the conveyance amount of the recording medium, and image data for calculating the movement amount of the movement amount measurement pattern, having an imaging area of a predetermined range with respect to the recording medium to be conveyed First imaging means for acquiring
It has an imaging area of a predetermined range arranged on the upstream side of the first imaging means in the transport direction, and selects a range for extracting the movement amount measurement pattern from the imaging areas of the first imaging means And a second imaging unit that acquires image data having a resolution lower than that of the first imaging unit. Selection means for selecting a range for extracting the movement amount measurement pattern from the entire imaging area of the first imaging means based on image data obtained from the second imaging means;
Based on the image data obtained from the area selected by the selection means, the movement amount measurement pattern is extracted, and the image extraction means for calculating the movement amount of the movement amount measurement pattern;
The transport amount measuring apparatus according to claim 1, further comprising a measurement unit that measures a transport amount of the recording medium from a travel amount of the travel amount measurement pattern.   The conveyance amount measuring apparatus according to claim 1, wherein an imaging region of the first imaging unit and an imaging region of the second imaging unit are adjacent to each other in the conveyance direction. A recording apparatus that includes a transport unit that transports a recording medium in a predetermined transport direction, and that records an image on the transported recording medium using a recording head,
Extraction of movement amount measurement pattern for measuring the conveyance amount of the recording medium, and image data for calculating the movement amount of the movement amount measurement pattern, having an imaging area of a predetermined range with respect to the recording medium to be conveyed First imaging means for acquiring
It has an imaging area of a predetermined range arranged on the upstream side of the first imaging means in the transport direction, and selects a range for extracting the movement amount measurement pattern from the imaging areas of the first imaging means And a second imaging unit that acquires image data having a resolution lower than that of the first imaging unit.

Images