JP2017026571A - Image processing system, image processing device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing system for measuring distribution of the reflection characteristics of a member to be measured.SOLUTION: An image processing system 10 includes: irradiation means 18 for irradiating a member 14 to be measured with light; imaging means 20 having a plurality of channels different from each other in sensitivity characteristics for receiving light irradiated from the irradiation means 18, and reflected by the member 14 to be measured; and synthesis means 48 for synthesizing a distribution image expressing distribution of the reflection characteristics of the member 14 to be measured on the basis of a plurality of images acquired by the plurality of channels of the imaging means 20.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a technique for measuring optical characteristics, and more particularly to an image processing system, an image processing apparatus, and a program for measuring a distribution of reflection characteristics of a member to be measured.

  2. Description of the Related Art In recent years, with an increasing demand for high added value of an image, an apparatus that can give gloss to a printed material has been provided. For example, a technique for imparting gloss using UV varnish that is cured by ultraviolet irradiation, a transparent ink that does not penetrate paper, and a technique for forming dots using transparent toner are known.

  From such a background, glossiness has become an important image quality characteristic along with image quality evaluation items such as color reproducibility and gradation reproducibility. Various techniques for evaluating the glossiness of printed matter and detecting the abnormality have been proposed. For example, Japanese Patent Laying-Open No. 2005-277678 (Patent Document 1) receives light diffusely reflected on the front side of paper and regular reflected light on the same front side with a line sensor, and gloss is obtained based on the obtained image. A technique for performing the inspection is disclosed.

  However, the intensity of the reflected light is relatively sensitive to the surface characteristics, especially in the specular reflection light conditions. Unlike the case where diffuse reflected light is captured, the illumination light quantity and imaging sensitivity are adjusted according to the characteristics of the member to be measured. It is necessary to shoot after adjusting. For example, when photographing an object having a rough surface and low glossiness and image clarity, a dark image will result unless the illumination light quantity is increased and the imaging sensitivity is not adjusted high. On the other hand, when shooting an object with high glossiness and image clarity, the image will be too bright unless the illumination light quantity is reduced and the imaging sensitivity is adjusted low. As described above, when the reflection characteristic such as gloss is to be evaluated, it is necessary to adjust the imaging system in accordance with the characteristics of the member to be measured. In addition, in the case of a member to be measured having a wide range of reflection characteristics in which various glosses are mixed, the measurement range is insufficient, and there may be black saturation or white saturation in a part of the image. It was difficult to get.

  On the other hand, if the sensitivity range of the measuring device is sufficiently wide, a member to be measured having a wide range of reflection characteristics can be evaluated by a single adjustment. Furthermore, if it can be obtained as a single distribution image, the result listability is improved. From such a background, development of a technique capable of generating a result representing the distribution of the reflection characteristics of the member to be measured as one distribution image and improving the listability while ensuring a wide sensitivity range of the measuring apparatus. It was desired.

  The present invention has been made in view of the insufficiency in the prior art described above, and the present invention uses a plurality of channels provided in the imaging means to expand the range in which the reflection characteristics of the member to be measured can be measured. However, an object of the present invention is to provide an image processing system capable of generating a measurement result having a high listability.

  In order to solve the above-described problems, the present invention provides an image processing system having the following characteristics for measuring the distribution of reflection characteristics of a member to be measured. The image processing system includes an irradiation unit that irradiates light to the member to be measured, and a plurality of channels each having a different sensitivity characteristic, and receives light that is irradiated from the irradiation unit and reflected by the member to be measured. Means. The image processing system further includes a combining unit that combines a distribution image representing the distribution of reflection characteristics of the member to be measured based on a plurality of images acquired by a plurality of channels of the imaging unit.

  With the configuration described above, it is possible to generate a measurement result with high listability while using a plurality of channels included in the imaging unit and expanding a measurable range of the reflection characteristics of the member to be measured.

The side view of the imaging system in the glossiness inspection system by this embodiment. The schematic block diagram of the control system in the glossiness inspection system by this embodiment. The figure explaining the glossiness stripe which is 1 type of glossiness noise. (A) The graph which shows typically the spectral characteristic of the illuminating device by this embodiment, and an imaging device, and the graph which shows typically the spectral characteristic as the whole imaging system of a B channel and a G channel (B, C). The flowchart which shows the calibration process which the glossiness inspection system by this embodiment performs. The figure which illustrates the calibration chart which can be used by this embodiment. The graph which plotted the given standard value of the glossiness of each patch area | region with respect to the measured value of each RGB channel measured in each patch area | region of the calibration chart shown in FIG. The figure which shows the estimation formula which approximates the relationship between the effective range of a measured value, a measured value, and glossiness with the measured value of each channel shown in FIG. 5 is a flowchart of gloss distribution measurement processing executed by the gloss inspection system according to the present embodiment. The figure which shows typically the surface of the printed matter in which the part which has various glossiness is mixed. The figure which shows the measured value of (A) each area | region measured with the printed matter shown in FIG. 10, and (B) the channel selected. The figure which shows typically the test | inspection image which shows the two-dimensional gloss distribution measured from the printed matter shown in FIG. The figure which shows the hardware constitutions of the image processing apparatus by specific embodiment.

  Hereinafter, although this embodiment is described, this embodiment is not limited to the embodiment described below. In the embodiment described below, as an example of an image processing system for measuring the distribution of reflection characteristics of a member to be measured, a gloss inspection system for inspecting the gloss distribution on the surface of a printed material based on a captured image is taken as an example. explain.

  FIG. 1 is a side view showing an imaging system of the gloss inspection system 10 according to the present embodiment. As shown in FIG. 1, the imaging system of the gloss inspection system 10 according to the present embodiment includes a regular reflection illumination device 18 for measuring gloss, a diffuse reflection illumination device 22 for measuring density, and a measurement target. And an imaging device 20 that receives reflected light from the surface and captures an image. Note that FIG. 1 schematically shows an imaging system of the gloss inspection system 10, and detailed illustration of other elements such as a mirror and a lens is omitted.

  The gloss inspection system 10 further includes a transport device 12 configured by, for example, a roller, and the transport device 12 transports the printed matter 14 as a member to be measured to the reading position 16. The printed material 14 is a medium such as paper on which an image is formed on the surface and gloss processing is performed on a part or all of the surface. The image and gloss forming surface of the printed material 14 become the measurement target surface. The reading position 16 is a reading area for one line where the reflected light distribution on the printed material surface is read by the imaging device 20. The printed material 14 is scanned in the sub-scanning direction indicated by the arrow by the conveying device 12 and read forward line by line.

The regular reflection illumination device 18 is not particularly limited, and is configured as an array of a plurality of reflective light emitting diodes, for example. The light emitted from the regular reflection illumination device 18 is incident on the entire area of the reading position 16 of the printed matter 14 at an incident angle θ ₁ through a mirror (not shown). This illumination light generates specularly reflected light at a reflection angle θ ₂ (θ ₁ = θ ₂ ) equal to the incident angle over the entire reading position 16 of the printed matter 14. The incident angle θ ₁ and the reflection angle θ ₂ are defined as angles with respect to the normal line of the measurement target surface of the printed matter 14 at the reading position 16.

The diffuse reflection illumination device 22 is not particularly limited, and for example, a xenon lamp or a light emitting diode can be used. The diffuse reflection illumination device 22 irradiates illumination light so as to be incident on the measurement target surface at the reading position 16 at a predetermined angle. Here, the predetermined angle is an angle different from the incident angle theta _1, typically it can be a normal direction, i.e. 0 ° measurement surface.

  The imaging device 20 is not particularly limited, and a line sensor that includes lines from a plurality of pixels, acquires the amount of incident light, and converts it into an electrical signal can be used. As the line sensor, for example, a CMOS (complementary metal oxide semiconductor), a CCD (charge coupled device), or the like can be used. In the embodiment to be described, details will be described later, but the imaging device 20 is configured to have a plurality of channels having different spectral sensitivity characteristics. Typically, a three-line type line sensor in which color filters for each of the three primary colors of RGB (red, green, and blue) are provided in each line can be used.

  Note that the RGB 3-line type line sensor is general-purpose and is preferable from the viewpoint of reducing the cost, but the specific configuration of the channel is not particularly limited. In another embodiment, a sensor having channels of three or more colors that can capture light of wavelengths that cannot be handled by infrared, ultraviolet, and other RGB three primary color filters may be used. In the embodiment described below, a line sensor that reads in one dimension is used as the imaging device 20, but the present invention is not particularly limited. In other embodiments, an image sensor that reads in two dimensions is used. May be.

  The imaging system including the imaging device 20 and the regular reflection illuminating device 18 has a geometry that allows the imaging device 20 to receive specularly reflected light that is irradiated from the regular reflection illuminating device 18 and specularly reflected on the surface of the printed matter at the reading position 16. Arranged so as to satisfy the desired conditions. Further, in the gloss inspection system 10, the diffuse reflection illumination device 22 is arranged so that a part of the diffuse reflection light diffusely reflected on the surface of the printed material satisfies a geometric condition that can be received by the imaging device 20. Although not particularly limited, in the exemplary embodiment, the specular reflection illumination device 18 illuminates the surface to be measured at 60 degrees with respect to the normal and receives light at 60 degrees with respect to the normal. Is done. Further, the diffuse reflection illumination device 22 can be configured to illuminate in the normal direction of the measurement target surface and receive light at an angle of 60 degrees with respect to the normal line.

  In the embodiment to be described, the regular reflection illumination device 18 and the diffuse reflection illumination device 22 are controlled to emit light alternately in accordance with the driving of the imaging device 20. For example, the regular reflection illumination device 18 and the diffuse reflection illumination device 22 are alternately blinked, and both the regular reflection light and the diffuse reflection light are captured by the imaging device 20 at a rate twice the blinking speed. It can be measured.

  FIG. 2 is a schematic configuration diagram of a control system of the gloss inspection system 10 according to the present embodiment. The image processing device 30 is a control device that controls the operation of each unit of the gloss inspection system 10. The regular reflection illumination device 18 and the diffuse reflection illumination device 22 are alternately turned on and off under the control of the image processing device 30. The conveyance device 12 conveys the printed material 14 intermittently or continuously in the sub-scanning direction under the control of the image processing device 30. Under the control of the image processing device 30, the imaging device 20 captures the distribution of the regular reflection light and the diffuse reflection light from the printed surface in accordance with the lighting of the regular reflection illumination device 18 and the diffuse reflection illumination device 22. To do.

  The image processing apparatus 30 is typically configured as a general-purpose computer, an image processing board, a controller unit, or a combination thereof. The image processing apparatus 30 includes an arithmetic device such as a CPU (Central Processing Unit), a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), and an HDD (Hard Disk Drive), a mouse, a keyboard, a display, and the like. An output device may be provided.

  As described above, the image processing apparatus 30 controls the operation of each part of the gloss inspection system 10 and captures an image read by the imaging apparatus 20 to inspect the gloss distribution and density distribution on the surface of the printed material that is the measurement target member. To do. The image processing apparatus 30 includes an inspection unit 40 for performing the above-described inspection, and the inspection unit 40 includes an illumination control unit 42 and an image acquisition unit 44. The inspection of the gloss distribution and the density distribution in the gloss inspection system 10 is typically performed as follows.

  First, the image processing device 30 causes the illumination control unit 42 to turn on the regular reflection illumination device 18 (while the diffuse reflection illumination device 22 is turned off), and irradiates the reading position 16 with illumination light. The imaging device 20 receives specularly reflected light from the printed material 14 and reads one line image (one-dimensional gloss distribution image) in each channel. The image processing device 30 acquires the read image from the imaging device 20 by the image acquisition unit 44 and stores the read image in the storage device. Subsequently, similarly, the illumination control unit 42 turns on the diffuse reflection illumination device 22 (while the regular reflection illumination device 18 is turned off), and irradiates the reading position 16 with illumination light. The imaging device 20 receives a part of the diffuse reflected light, and reads one line image (one-dimensional density distribution image) in each channel. The image acquisition unit 44 acquires the read image from the imaging device 20 and stores it in the storage device.

  Next, the transport device 12 transports the printed material 14 by a predetermined distance in the sub-scanning direction indicated by the arrow, and the same operation as described above is performed for the next line. By repeating the same operation for each line, a two-dimensional gloss distribution image and a two-dimensional density distribution image of the entire printed matter 14 are formed on the storage device of the image processing apparatus 30. Here, the two-dimensional gloss distribution image mainly means the distribution of specular reflection light of the printed matter 14, and the two-dimensional density distribution image mainly means the distribution of diffuse reflection light of the printed matter 14. In the above description, the imaging and conveyance are described as being performed intermittently. However, the printed matter 14 is continuously conveyed, and the regular reflection illumination device 18 and the diffuse reflection illumination device 22 are alternately turned on. Alternatively, the surface of the printed material 14 may be continuously imaged.

  Based on the two-dimensional gloss distribution image and the two-dimensional density distribution image stored in the storage device by the inspection unit 40, the image processing apparatus 30 covers the gloss distribution and the density distribution over the entire area of the printed material 14 that is a measurement target member. Inspect. For example, based on these images, the inspection image obtained as the inspection result can be displayed on a display, saved in a file, or the detection result of noise such as gloss streaks or uneven glossiness can be displayed by image analysis. Can do.

  The gloss streak is a streak-like gloss noise as shown in FIG. 3 that appears when a printed material is observed under specular reflection conditions. The gloss streaks appear in a form in which the gloss increases in the two-dimensional gloss distribution image as compared to the surrounding images due to wear of the heating roll or the guide during conveyance. Gloss nonuniformity refers to macro unevenness due to gloss fluctuations between pages and within a page, and gloss fluctuations due to the amount of color material and area ratio. In addition, there are gloss noises such as gloss unevenness due to a small gloss difference, a non-image portion and between image portions, and a step difference in the vicinity of the boundary between image portions.

  At this time, the density distribution can be configured as a color image of RGB multiple channels. On the other hand, with respect to the gloss distribution, the glossiness can be expressed only by any one channel information, and therefore a two-dimensional gloss distribution image may be configured as any one channel image depending on conditions.

  However, when measuring a member to be measured having a wide range of gloss, the measurement range may be insufficient with one channel. For example, in the case of a catalog or the like, there are cases where the paper quality differs depending on the page, varnishing or processing is performed to give gloss, or partial processing is performed only on the portion of the page where gloss is desired. In such a case, the gloss distribution cannot be accurately expressed with one channel.

  Therefore, in the present embodiment, paying attention to the fact that the spectral sensitivity characteristics of each channel of the imaging device 20 are different, when measuring a two-dimensional gloss distribution image, based on a plurality of images acquired by a plurality of channels having different sensitivities. A configuration is adopted in which a distribution image representing the distribution of reflection characteristics of the member to be measured is synthesized.

  More specifically, the image processing apparatus 30 according to the embodiment to be described is configured to further include a calibration unit 46 and a measurement unit 48 in the inspection unit 40 in relation to the above-described measurement of the gloss distribution image. . The calibration unit 46 grasps the characteristics of the regular reflection illumination device 18 and the imaging device 20 so that a wide range of glossiness can be measured. The measurement unit 48 is a single distribution that collectively represents the distribution of the reflection characteristics of the member to be measured based on the plurality of images acquired by the plurality of channels of the imaging device 20 based on the characteristics grasped by the calibration unit 46. Composite the images. The calibration unit 46 constitutes a determination unit in the present embodiment, and the measurement unit 48 constitutes a synthesis unit in the present embodiment.

  FIG. 4A is a graph schematically showing spectral characteristics of the regular reflection illumination device 18 and the imaging device 20 according to the present embodiment. As shown in FIG. 4A, the light emission intensity (or energy) of the regular reflection illumination device 18 has frequency (wavelength) dependence, and each channel of the image pickup device 20 similarly has a solid-state image pickup device itself. Due to sensitivity characteristics and filter characteristics, it has frequency (wavelength) -dependent spectral sensitivity characteristics. The intensity of light sensed by the RGB sensor elements of the imaging device 20 under a certain illumination condition depends on the spectral characteristics of the light source of the regular reflection illumination device 18 and the spectral sensitivity characteristics of each channel, that is, Therefore, it depends on the spectral characteristics of the entire imaging system including the illumination system and the light receiving system.

  Therefore, when the spectral distribution as shown in FIG. 4A is given, the multiplied spectral characteristics are as shown in FIG. 4B for the B channel and as shown in FIG. C). As understood with reference to FIGS. 4B and 4C, when imaging regular reflection light, the B channel is stronger than the G channel even if illumination is performed with the same amount of illumination. Regularly reflected light is detected.

  Comparing the G and B channels, a portion with relatively high glossiness and image clarity means that an image captured with the G channel having a relatively low effective sensitivity is more appropriate. On the other hand, in a portion where glossiness and image clarity are relatively low, an image captured by the B channel having a relatively high effective sensitivity is more appropriate.

  Therefore, in a specific embodiment, a channel with high sensitivity is assigned to a portion with low glossiness and low image clarity, and a channel with low sensitivity is assigned to a portion with high glossiness and high image clarity. can do. As a result, it is possible to measure glossiness and image clarity in a wide range, and to generate a distribution image with high listability.

  In the embodiment to be described, as shown in FIG. 4A, the regular reflection illumination device 18 uses a blue LED (Light Emitting Device) having a peak around 450 nm, and the imaging device 20 has RGB3. The case where a line type line sensor is used will be described. Although the spectral sensitivity characteristics of the R channel are not shown in FIG. 4, it can be said that the R channel has lower sensitivity than the G channel because the illuminating device 18 having a wavelength of 620 to 750 nm corresponding to the R channel has low emission intensity. . Therefore, it is preferable that the R channel is in charge of a portion with higher glossiness and higher image clarity.

  The specific spectral characteristics of each channel of the regular reflection illumination device 18 and the imaging device 20 are not particularly limited. Needless to say, the present invention can be similarly applied to an illumination device having a peak in a different specific frequency band or a plurality of channels having spectral sensitivity characteristics different from those of RGB.

  Hereinafter, the calibration process in the gloss inspection system 10 according to the present embodiment will be described with reference to FIGS. FIG. 5 is a flowchart showing the calibration process executed by the gloss inspection system 10 according to the present embodiment. In the following, calibration processing for gloss measurement under regular reflection conditions will be described, and unless otherwise specified, the regular reflection illumination device 18 is simply referred to as the illumination device 18.

  The process shown in FIG. 5 is started from step S100 in response to the activation of the system or an instruction to start calibration from the operator. In step S101, the image processing apparatus 30 performs initial adjustment including adjustment of the amount of illumination light. In the initial adjustment, the image processing device 30 can adjust the illumination light amount of the illumination device 18 using the channel with the lower effective sensitivity based on the spectral characteristics of the illumination device 18 and the imaging device 20. For adjustment of the amount of illumination light, a high gloss reference member with high glossiness and image clarity is prepared, and the distribution of the specular reflection light of the high gloss reference member can be appropriately measured in the channel with the lower effective sensitivity. To be done. By adjusting the amount of illumination light in this way, adjustment can be performed once so that a member to be measured having a wide range of image clarity and glossiness can be photographed. Although only the illumination light amount is adjusted here, the aperture of the imaging lens may be adjusted.

  In step S <b> 102, the image processing apparatus 30 captures a predetermined calibration chart with the imaging apparatus 20, and acquires an image for calibration acquired from the calibration chart in each channel of the imaging apparatus 20 with the image acquisition unit 44.

  FIG. 6 illustrates a calibration chart that can be used in this embodiment. The calibration chart shown in FIG. 6 includes a plurality of belt-like patch regions each having different reflection characteristics (glossiness and image clarity). The calibration chart can be prepared by printing a plurality of patch areas having various glossiness and image clarity depending on the amount of pigment and the material at the time of printing. The smaller the steps of glossiness and image clarity, the more processing time and labor are required, but the measurement accuracy can be improved. Here, it is assumed that the glossiness and image clarity of the calibration chart are previously measured for each patch area, and the features of each patch are clear (that is, the gloss evaluation value is known). .

  Here, the glossiness represents the psychological glossiness or glossiness of the printed material surface. The image clarity (image sharpness) represents the sharpness of an image reflected on the surface. As a method for measuring gloss, a specular gloss measurement method for measuring the intensity of specular reflection light (regular reflection light) defined by JIS Z 8741 is known. In addition, an evaluation method using diffuse reflection light other than regular reflection light is also known. As a method for measuring image clarity, for example, a method defined in JIS K 7374 is known. In the embodiment to be described, specular gloss at 60 ° (hereinafter simply referred to as gloss) Gs (60 °) defined by JIS Z 8741 is used as the glossiness evaluation value.

By the above-described step S102, a set of measurement values (measurement value _{R 1} , measurement value _{G 1} , measurement value _{B 1} ) acquired in a plurality of channels in each of a plurality of patch regions is acquired. FIG. 7 shows a graph in which a given standard value of the glossiness of each patch area is plotted against the measurement values of each RGB channel measured in each patch area of the calibration chart shown in FIG. Note that calibration data is prepared for Gs (60 °) low gloss to high gloss measurement targets. According to the graph shown in FIG. 7, it is possible to associate a portion having a certain glossiness as the signal intensity observed in each channel, and the signal intensity of each channel is within the range of the lower limit value or the upper limit value. The measurable range is also grasped. Then, by using the result, it is possible to set conditions for selecting an appropriate channel for each part at the time of measurement.

  In steps S <b> 103 and S <b> 104, an estimation formula for glossiness that changes depending on the spectral distribution and light amount of the illumination device 18 and the spectral sensitivity of the imaging device 20 is obtained based on the calibration data obtained from the acquired calibration image.

  In step S103, the image processing apparatus 30 uses the calibration unit 46 to determine a glossiness range that can be measured for each RGB channel from the calibration data (a set of measurement values for each patch area) obtained in step S102. FIG. 7 plots the relationship between the measured values of the image acquired as described above and the standard values of the glossiness of the patches. The B channel is generally linear in the low gloss range, the G channel is generally linear in the medium gloss range, and the R channel is mainly in the high gloss range. It is understood that the part is generally linear.

  An example of the effective range determination method is not particularly limited, but can be performed by setting an upper limit and a lower limit for the measured value as shown in FIG. First, the glossiness portion that is not appropriate to be measured in each channel corresponds to a case where the measured value is near 0 (that is, corresponds to black saturation) and a case where the measurement value is near 255 (that is, corresponds to white saturation). .). For this reason, it is possible to determine a valid range by taking a predetermined margin, for example, by measuring only 20 to 220 portions where the measured value is 8 bits. In the example shown in FIGS. 7 and 8, when determined from the range of measurement values, the B channel has an effective range of Gs (60 °) of 5 to 25, and the G channel has an Gs (60 °) of 25 to 25. The range of 55 is effective, and it can be said that the R channel is effective when the Gs (60 °) is in the range of 55 to 75. Preferably, the effective range of the measurement value is determined so that the entire range of glossiness to be measured is covered by summing up a plurality of RGB channels.

  In step S104, the image processing apparatus 30 uses the calibration unit 46 to obtain a glossiness estimation formula that approximates the relationship between the measurement value and the glossiness of each channel based on the effective range determined in step S103. More specifically, in step S104, a standard value of a given glossiness for each of a plurality of patch areas of the calibration chart and a set of measurement values acquired by a plurality of channels in each of the plurality of patch areas. Based on this, the coefficient (estimation parameter) of the glossiness estimation formula is determined.

  First, a case where the measurement values of the RGB channels are linearly approximated corresponding to the glossiness will be described. In the calibration data plots shown in FIGS. 7 and 8, only one measurement point is plotted for each patch for convenience of explanation. However, in the calibration chart shown in FIG. 6, measurement values corresponding to the width of the patch area are obtained, and therefore, the coefficient of the estimation formula is calculated using the measurement values within the effective range among these many measurement values. Can be calculated.

  For example, using the least square method for determining a coefficient that minimizes the sum of squares of the residual between the estimated value calculated from the estimated expression and a given standard value, the following estimated expression (1) The coefficient of (3) can be calculated | required. FIG. 8 shows an estimation formula for glossiness that linearly approximates the measurement points obtained from the example calibration data.

(Equation 1)
B channel: Gloss level = a _B × measured value _B + b _B (20 ≦ measured value _B ≦ 220) (1)
G channel: Gloss level = a _G × measured value _G + b _G (20 ≦ measured value _G ≦ 220) (2)
R channel: Glossiness = a _R × Measured value _R + b _R (20 ≦ Measured value _R ≦ 220) (3)

  The estimation formula described above shows a case of linear approximation, and the estimation formula is selected corresponding to the range of effective measurement values of each RGB. The accuracy of the estimated value can be improved by increasing the number of patch areas in the calibration chart and making the glossiness step finer. In addition, when performing linear approximation, the estimation parameter further includes an effective measurement value range of each channel. In the above example, the effective measurement value range is set to 20 to 220 assuming that the measurement value is 8 bits.

  In the example of the estimation equation, the lower limit of the measurement value is set to 20 for the B channel. However, it may be set to 0 because the low glossiness is included in the range. For the R channel, the upper limit of the measurement value is 220, but it may be 255 because high glossiness is also included in the range. Further, in the embodiment to be described, the measurement value is described as being 8 bits. However, in other embodiments, the measurement value may be measured with other gradation numbers such as 10 bits or 16 bits. In that case, the effective range may be determined by a value corresponding to the number of gradations.

  In addition to linear approximation, without setting the effective range of the B channel, the G channel, and the R channel, the glossiness estimation value is obtained from a set of measurement values acquired from a plurality of channels represented by the following formula from the calibration data. It is also possible to obtain an estimation formula that gives the value and directly obtain it from the following formula (4).

(Equation 2)
Gloss level = c _B × Exp (measured value _B ) ^ d _B + c _G × Exp (measured value _G ) ^ d _G + c _R × Exp (measured value _R ) ^ d _R (4)

  When the estimation formula is obtained in step S104, the calibration process is terminated in step S105, and the measurement preparation is completed.

  Hereinafter, the gloss measurement process in the gloss inspection system 10 according to the present embodiment will be described with reference to FIGS. 9 to 12. FIG. 9 shows a flowchart of the gloss measurement process executed by the gloss inspection system 10 according to the present embodiment. FIG. 9A shows a gloss measurement process when using a plurality of estimation formulas prepared for each of a plurality of channels by the above-described linear approximation. On the other hand, FIG. 9B shows gloss measurement processing in the case of using a single estimation formula prepared for the plurality of channels described above.

  Hereinafter, a description will be given first with reference to FIG. The process shown in FIG. 9A is started from step S200 in response to an instruction to start an inspection from the user after the measurement preparation is completed in step S105 shown in FIG.

  In step S <b> 201, the image processing apparatus 30 images the measurement target member with the imaging apparatus 20, and acquires a two-dimensional gloss distribution image acquired with each channel of the imaging apparatus 20 by the image acquisition unit 44. FIG. 10 schematically shows the surface of a printed material in which various glossy portions are mixed. Here, a description will be given assuming that the member to be measured is a printed material including three regions having different glossinesses as shown in FIG.

  In steps S202 to S205, the processes of steps S203 and S204 are executed for each pixel constituting the two-dimensional gloss distribution image.

  In step S <b> 203, the image processing apparatus 30 causes the measurement unit 48 to select a channel to be used based on a set of RGB measurement values of the target pixel. In the case of the printed matter shown in FIG. 10, as a result of photographing the two-dimensional gloss distribution image, a distribution of a set of measurement values as shown in FIG. 11A is obtained. When a channel used for measurement is selected from the set of measurement values of each pixel shown in FIG. 11A based on the above-described effective measurement value range, the result is as shown in FIG. 11B.

In step S <b> 203, the image processing apparatus 30 causes the measurement unit 48 to calculate an estimated value of glossiness based on the measurement value corresponding to the selected channel and the glossiness estimation formula. For example, in the printed matter shown in FIG. 10, the B channel is selected for the region indicated by a circle, and the estimated glossiness value is calculated from the measured value _B of the B channel by the above equation (1).

  When the effective measurement value range falls within a plurality of channels, an estimated value of glossiness can be calculated using an estimation formula for the channel farther from the upper limit or the lower limit. Alternatively, the glossiness estimation value can be calculated by averaging or weighted averaging the glossiness estimation values obtained by a plurality of corresponding estimation equations.

  After exiting the pixel-by-pixel loop from step S202 to step S205, in step S206, the image processing apparatus 30 stores a two-dimensional gloss distribution including the calculated glossiness estimation value as a pixel value as an inspection image, and step S207. This process is finished. By obtaining an estimated value of glossiness using the estimation formula of each channel and inputting the estimated value of glossiness calculated as a pixel value instead of the measured value, a two-dimensional gloss distribution as shown in FIG. 12 is obtained. can get

  Hereinafter, description will be continued with reference to FIG. The process shown in FIG. 9B is started from step S300 as in FIG. 9A. In step S <b> 301, the image processing device 30 acquires a two-dimensional gloss distribution image acquired in each channel of the imaging device 20. In step S302 to step S304, the process of step S303 is executed for each pixel.

In step S <b> 303, the image processing apparatus 30 causes the measurement unit 48 to calculate an estimated value of glossiness based on a set of RGB measurement values of the target pixel. Here, no particular channel is selected, and an estimated value of glossiness is calculated from a set of measurement values (measurement value _{R 1} , measurement value _{G 1} , measurement value _B 2) by the above equation (4).

  After exiting the pixel-by-pixel loop from step S302 to step S304, in step S305, the image processing apparatus 30 stores the final two-dimensional gloss distribution as an inspection image, and the process ends in step S306. Similarly, two-dimensional as shown in FIG. 12 is obtained by obtaining an estimated value of glossiness using a single estimation formula and inputting the estimated value of glossiness calculated as a pixel value instead of the measured value. A gloss distribution is obtained.

  Hereinafter, the hardware configuration of the image processing apparatus 30 according to the specific embodiment will be described with reference to FIG. FIG. 13 is a diagram illustrating a hardware configuration of the image processing apparatus 30 according to a specific embodiment. The image processing apparatus 30 according to the present embodiment is configured as a general-purpose computer such as a desktop personal computer or a workstation. An image processing apparatus 30 shown in FIG. 13 includes a CPU (Central Processing Unit) 112, a north bridge 114 that is connected to the CPU 112 and a memory, and a south bridge 116 that is connected to an I / O such as a PCI bus or USB. Are configured on the board 110.

  The north bridge 114 is connected to a RAM (Random Access Memory) 118 that provides a work area for the CPU 112 and a graphic board 120 that outputs a video signal. The graphic board 120 is connected to the display 140 via a video output interface.

  The south bridge 116 includes a peripheral component interconnect (PCI) 122, a LAN port 124, an IEEE (the Institute of Electrical and Electronics Engineers, Inc.) 1394 port 126, a universal serial bus (USB) port 128, a hard disk drive (HDD). ) And SSD (Solid State Drive), an auxiliary storage device 130, an audio input / output 132, and a serial port 134 are connected. The auxiliary storage device 130 stores an OS for controlling the computer device, a control program for realizing the above-described functional units, various system information, and various setting information. The LAN port 124 is an interface device that connects the image processing apparatus 30 to the LAN.

  Input devices such as a keyboard 142 and a mouse 144 may be connected to the USB port 128, and a user interface for accepting input of various instructions from an operator of the image processing apparatus 30 can be provided. The image processing apparatus 30 according to the present embodiment reads the control program from the auxiliary storage device 130 and develops it in the work space provided by the RAM 118, thereby realizing the above-described functional units and processes under the control of the CPU 112.

  According to the embodiment described above, image processing that can generate a measurement result with high listing properties while expanding the measurable range of the reflection characteristic of the member to be measured by utilizing a plurality of channels included in the imaging unit. A system, an image processing apparatus, and a program can be provided.

  As described above, in the multiple channels for capturing density images, the glossiness that can be measured in each channel differs depending on the spectral distribution of illumination due to the influence of the spectral distribution of illumination. The range of is different. In the embodiment described above, the measurable range is expanded by utilizing the characteristics of the plurality of channels described above. For this reason, even a subject having a wide range of gloss can be measured. Further, the obtained gloss distribution is not divided into a plurality of channel images, but is collected as a single image, so that information at the boundary is not divided, and the list of measurement results is improved.

  Further, in the preferred embodiment described above, a gloss image can be measured by utilizing a plurality of color channels used for density images, so that instrumentation costs can be reduced.

  In the above-described embodiment, the printed material on which an image is formed is described as an example of the member to be measured. However, the member to be measured is not necessarily limited to the printed material. In other embodiments, it may be a transfer member such as a sheet before transfer, a photographic printing paper, a coating film, or a colored metal. In the above-described embodiment, the distribution of specular reflection light is measured as a gloss distribution image, but this does not preclude taking into account the measurement result of diffuse reflection light in the gloss evaluation.

  The functional unit can be realized by a computer-executable program written in a legacy programming language such as an assembler, C, C ++, C #, Java (registered trademark), an object-oriented programming language, or the like. ROM, EEPROM, EPROM , Stored in a device-readable recording medium such as a flash memory, a flexible disk, a CD-ROM, a CD-RW, a DVD-ROM, a DVD-RAM, a DVD-RW, a Blu-ray disc, an SD card, an MO, or through an electric communication line Can be distributed. In addition, a part or all of the functional unit can be mounted on a programmable device (PD) such as a field programmable gate array (FPGA) or mounted as an ASIC (application-specific integration). Circuit configuration data (bit stream data) downloaded to the PD in order to implement the above functional unit on the PD, HDL (Hardware Description Language) for generating the circuit configuration data, VHDL (VHSIC (Very High Speed) Integrated Circuits) Hardware Description Language), Verilog-HDL, etc., can be distributed on recording media as data.

  Although the embodiments of the present invention have been described so far, the embodiments of the present invention are not limited to the above-described embodiments, and those skilled in the art may conceive other embodiments, additions, modifications, deletions, and the like. It can be changed within the range that can be done, and any embodiment is included in the scope of the present invention as long as the effects of the present invention are exhibited.

DESCRIPTION OF SYMBOLS 10 ... Gloss inspection system, 12 ... Conveyance device, 14 ... Printed matter, 16 ... Reading position, 18 ... Illumination device for regular reflection, 18 ... Illumination device, 20 ... Imaging device, 22 ... Illumination device for diffuse reflection, 30 ... Image processing Device: 40 ... Inspection unit, 42: Illumination control unit, 44 ... Image acquisition unit, 46 ... Calibration unit, 48 ... Measurement unit, 110 ... Board, 112 ... CPU, 114 ... Northbridge, 116 ... Southbridge, 118 ... RAM 120 ... Graphic board, 122 ... PCI, 124 ... LAN port, 126 ... IEEE1394 port, 126 ... NV-RAM, 128 ... USB port, 130 ... Auxiliary storage device, 132 ... Audio input / output, 134 ... Serial port, 140 ... Display, 142 ... Keyboard, 144 ... Mouse

JP 2005-277678 A

Claims (10)

An image processing system for measuring the distribution of reflection characteristics of a member to be measured,
Irradiating means for irradiating light to the member to be measured;
An imaging unit having a plurality of channels each having a different sensitivity characteristic, and receiving light irradiated from the irradiation unit and reflected by the member to be measured;
An image processing system comprising: a combining unit configured to combine a distribution image representing a distribution of reflection characteristics of the member to be measured based on a plurality of images acquired by the plurality of channels of the imaging unit.   The image processing system according to claim 1, wherein the synthesizing unit calculates an estimated value of reflection characteristics for each pixel based on a set of measurement values acquired by the plurality of channels. An acquisition means for acquiring a set of calibration measurement values acquired in the plurality of channels in each of the plurality of regions based on a calibration chart having a plurality of regions each having different reflection characteristics;
Based on the standard value of the reflection characteristic given for each of the plurality of areas of the calibration chart and the set of the measurement values for calibration acquired by the plurality of channels in each of the plurality of areas, The image processing system according to claim 2, further comprising: a determining unit that determines an estimation parameter, wherein the combining unit calculates an estimated value of the reflection characteristic based on the estimation parameter. The estimation parameter includes an effective measurement value range of each of the plurality of channels, and a coefficient of an estimation formula that gives an estimated value of reflection characteristics from the measurement values for each of the plurality of channels,
The synthesizing unit calculates an estimated value of the reflection characteristic based on a measured value corresponding to a channel selected according to a set of measured values acquired in the plurality of channels and a coefficient of the estimation equation. Item 4. The image processing system according to Item 3. The estimation parameter includes a coefficient of an estimation formula that gives an estimation value of a reflection characteristic from a set of measurement values acquired in the plurality of channels,
The image processing system according to claim 3, wherein the synthesizing unit calculates an estimated value of the reflection characteristic based on a set of measurement values acquired in the plurality of channels and a coefficient of the estimation formula.   The image processing system according to claim 1, wherein each of the plurality of channels has a spectral characteristic different from each other, and the irradiation unit has a peak in a specific frequency band.   The image processing system according to claim 6, wherein the plurality of channels include a red channel, a green channel, and a blue channel.   The member to be measured is a transfer member to which gloss is given, and the imaging unit and the irradiating unit are configured to receive the light irradiated from the irradiating unit and regularly reflected on the surface of the transfer member. The image according to claim 1, wherein the reflection characteristic is glossiness, and the distribution image is a two-dimensional distribution of gloss. Processing system. An image processing apparatus for measuring a distribution of reflection characteristics of a member to be measured,
Control means for controlling the member to be measured to emit light by means of irradiation means;
A plurality of images picked up by the plurality of channels are received by the image pickup means by receiving the light irradiated by the irradiation means and reflected by the member to be measured from the image pickup means having a plurality of channels having different sensitivity characteristics. Acquisition means for acquiring;
An image processing apparatus comprising: a combining unit configured to combine a distribution image representing a distribution of reflection characteristics of the member to be measured based on the plurality of images acquired by the acquiring unit. A program for realizing an image processing device for measuring the distribution of reflection characteristics of a member to be measured, comprising:
Control means for controlling the irradiated member to emit light to the member to be measured;
A plurality of images picked up by the plurality of channels are received by the image pickup means by receiving the light irradiated by the irradiation means and reflected by the member to be measured from the image pickup means having a plurality of channels having different sensitivity characteristics. An acquisition means for obtaining, and a program for functioning as a synthesis means for synthesizing a distribution image representing a distribution of reflection characteristics of the member to be measured based on the plurality of images obtained by the obtaining means.