Patent Application
20190331600
The present invention relates to a measurement apparatus, an information processing apparatus, an information processing method, and a storage medium.
Surfaces such as printing surfaces, coating surfaces, and the outer surfaces of products are evaluated based on a plurality of types of reflection characteristics (index values) of the surfaces. The plurality of types of reflection characteristics are defined by JIS and ISO standards, and can include specular gloss, haze, DOI (Distinctness of Image), and image clarity. PTL 1 proposes a measurement apparatus that measures a plurality of types of reflection characteristics like those described above.
As a surface reflection characteristic index (indicating a reflection characteristic), a BRDF (Bidirectional Reflectance Distribution Function) is available. A BRDF is an index indicating with what intensity distribution light entering a surface is reflected (the intensity distribution of reflected light), and is useful to evaluate or check a reflection characteristic of light on a measurement surface. Conventionally, however, the BRDF has not been effectively used to evaluate an outer appearance associated with a reflection characteristic of a surface.
It is therefore an exemplary object of the present invention to provide a measurement apparatus advantageous in evaluating a reflection characteristic of a surface.
PTL 1: Japanese Patent Laid-Open No. 2014-126408
According to one aspect of the present invention, there is provided a measurement apparatus comprising: an irradiation unit configured to obliquely irradiate a surface with light; a detection unit configured to detect an intensity distribution of reflected light from the surface; a processing unit configured to determine a BRDF of the surface based on the intensity distribution, and generate a first image representing the determined BRDF as a two-dimensional distribution and a second image representing a one-dimensional distribution obtained by projecting the two-dimensional distribution of the determined BRDF in a predetermined direction; and a display unit configured to display the first image and the second image generated by the processing unit, wherein the processing unit is configured to generate the first image representing the BRDF as the two-dimensional distribution in which an ordinate axis and an abscissa axis are two directions respectively orthogonal to an optical axis of specular light.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the same reference numerals denote the same members and elements throughout the drawings, and any redundant description will be omitted.
The arrangement of a measurement system 100 (measurement apparatus) according to the present invention will be described with reference to
The measurement apparatus 10 can include, for example, a measurement unit 12, an output unit 13, an input unit 14 (operation unit), and the control unit 15, and measures a reflection characteristic of a measurement surface 20. The measurement unit 12 is provided in a housing 11 (inside the housing) and measures a reflection characteristic of the measurement surface 20 via an opening portion provided in the lower surface of the housing 11 while outside light is blocked by the housing 11. The output unit 13 outputs an image onto a display unit 13a such as an LCD provided on the upper surface of the housing. That is, the output unit 13 can function as a display control unit that causes the display unit 13a to display a reflection characteristic of a measurement surface. The input unit 14 receives various settings from a user via a plurality of buttons 14a provided on the upper surface of the housing 11. The input unit 14 according to this embodiment includes the plurality of buttons 14a. However, this is not exhaustive. For example, the display unit 13a (display) provided on the upper surface of the housing 11 may be of a touch panel type. That is, the input unit 14 may include the touch panel type display unit 13a. The control unit 15 includes a processing unit 15a including a CPU and a storage unit 15b including a memory, and controls the measurement unit 12, the output unit 13, and the input unit 14. In addition, the measurement apparatus 10 has a power button 16 and a communication I/F 17 (USB port) provided on the housing 11 (its side surface).
The arrangement of the measurement unit 12 and a method of measuring reflection characteristics (a plurality of types of index values) of the measurement surface 20 using the measurement unit 12 will be described next with reference to
The light beam emitted from the light source 12a is collected in the slit 12c by the lens 12b. An image of the light source 12a is temporarily formed in the slit 12c to become a rectangular secondary light source. A light beam exiting from the slit 12c becomes a divergent light beam again and is collimated by the lens 12d to irradiate the measurement surface 20. Reflected light from the measurement surface 20 is formed into a reflection pattern unique to the reflection characteristics of the measurement surface 20. The light is then collected by the lens 12e and received by the light-receiving surface of the sensor 12f. The sensor 12f includes an area sensor including a two-dimensional array of photoelectric conversion elements constituted by CCDs or CMOSs. The intensity distribution of reflected light formed on the light-receiving surface of the sensor 12f becomes a reflection pattern whose intensity changes in accordance with an angle as indicated by the inside of the broken line in
As one of the indices representing reflection characteristics of the measurement surface 20, a BRDF (Bidirectional Reflectance Distribution Function) is available. One method of obtaining a BRDF based on the intensity distribution of reflected light detected by the detection unit is described in, for example, Japanese Patent Laid-Open No. 2016-211999. The control unit 15 (processing unit 15a) obtains the Fourier transform of a BRDF by dividing the Fourier transform of the intensity distribution of the reflected light detected by the detection unit by the Fourier transform of slit information. The BRDF of the measurement surface 20 can be obtained by performing the inverse Fourier transform of the obtained Fourier transform. A BRDF is a function representing the distribution of reflectances of a measurement surface, and represents the ratio of the luminance of reflected light to the illuminance of incident light. In a more strict sense, a BRDF at a given point on an object surface is dependent on both incident and reflection directions and defined as the ratio of the intensity of reflected light (diffused light) to the intensity of incident light from an irradiation direction. That is, as shown in
Indices representing reflection characteristics of the measurement surface 20 include, other than a BRDF, a specular gloss, haze, DOI (Distinctness of Image), image clarity, reflectance, and undulation. Several of these indices will be described. A specular gloss represents the light amount of a specular component. A haze represents the distribution of light around a specular component. A DOI and image clarity indicate a reduction in contrast of a glare image. A specular gloss, haze, DOI, and image clarity can be acquired or generated (calculated) based on an intensity distribution as a blurred image of a rectangular slit instead of a BRDF as a point image distribution function. Accordingly, the control unit 15 (processing unit 15a) can obtain these index values by referring to a table or performing convolution of apparatus information based on the intensity distribution of reflected light detected by the detection unit.
In this case, an incident angle θ (a reflection angle θ′ of reflected light from the measurement surface 20) of light with which the measurement surface 20 is irradiated by the irradiation unit at the time of measurement of reflection characteristics of the measurement surface 20 is defined for each reflection characteristic index (standard) according to JIS, ISO, or the like. Accordingly, when, for example, a mirror gloss is to be measured as a reflection characteristic index, the incident angle θ is set to any one of 20°, 45°, 60°, 75°, and 85°. In addition, when a haze is to be measured as a reflection characteristic index, the incident angle θ is set to 20°or 30°. When an image clarity is to be measured as a reflection characteristic index, the incident angle θ is set to 45° or 60°. When a DOI is to be measured as a reflection characteristic index, the incident angle θ is set to 20° or 30°. The measurement unit 12 may be provided with a plurality of pairs of irradiation units and detection units so as to set different incident angles θ or provided with a driving unit that drives an irradiation unit and a detection unit so as to change the incident angle θ.
The plurality of types of index values (BRDF, mirror gloss, haze, DOI, image clarity, and the like) obtained by the processing unit 15a in this manner are stored in the storage unit 15b in association with each other.
The user checks the reflection tendency of light at the measurement surface 20 by referring to a BRDF indicating with what intensity distribution light entering the measurement surface 20 is reflected (the intensity distribution of reflected light). At this time, it is preferable in terms of user convenience to display the BRDF so as to allow the user to easily and quickly check the reflection tendency of the measurement surface 20 only by giving one glance at the display of the BRDF. Accordingly, the measurement system 100 obtains the two-dimensional BRDF of the measurement surface 20 based on the intensity distribution of reflected light detected by the measurement unit 12 (detection unit), and displays the obtained two-dimensional BRDF on the display unit 13a (or the display unit 18f).
In this case, the measurement unit 12 (detection unit) detects the intensity distribution of reflected light in the range of predetermined directions, of the directions of reflected light from the measurement surface 20, which include a first direction 21 as the direction of specular light from the measurement surface 20. As shown in
The range of the predetermined directions corresponds to the range of 0° to 90° as the range of the reflection angles of reflected light from the measurement surface 20. That is, the range of the predetermined directions is the range of the directions of reflected light with reflection angles larger than 0° and smaller than 90°. In addition, the range of the predetermined directions includes a range on a first plane (an incident plane (for example, the drawing surface)) including specular light and a second plane (for example, a plane orthogonal to the drawing surface) including specular light. That is, the range of predetermined directions is defined on each of the first plane and the second plane.
Specific embodiments will be described below.
A processing unit 15a according to this embodiment generates an image (to be referred to as a two-dimensional image hereinafter) representing the BRDF, as a two-dimensional gradation distribution, which is obtained based on the detection result (the intensity distribution of reflected light) obtained by the detection unit in the above manner. An output unit 13 outputs (causes the display unit 13a to display) the two-dimensional image generated by processing unit 15a to a display unit 13a.
In this case, the user often wants to check the details of a BRDF near specular light. Accordingly, the processing unit 15a preferably generates a two-dimensional image such that part of the obtained BRDF which corresponds to a specular direction is arranged in a central portion of the two-dimensional image. At this time, the processing unit 15a preferably generates a two-dimensional image in a range in which the reflection angle of reflected light is equal to or more than 0° and equal to or less than 90°. Specular light is reflected light having a reflection angle θ′ equal to an incident angle θ of light applied on a measurement surface (that is, the reflection angle θ′ of specular light is equal to the incident angle θ). The central portion of a two-dimensional image is a region including the center of the two-dimensional image.
In this embodiment, the processing unit 15a of a measurement apparatus 10 generates a two-dimensional image. However, this is not exhaustive, and a processing unit 18a of an information processing apparatus 18 may generate a two-dimensional image by acquiring the detection result obtained by the detection unit from the a control unit 15 (storage unit 15b). In addition, in the embodiment, the output unit 13 of the measurement apparatus 10 outputs a two-dimensional image to the display unit 13a. However, this is not exhaustive. For example, the output unit 13 may output a two-dimensional image to a display unit 18f provided outside the measurement apparatus 10 (housing 11) or an output unit 18c of the information processing apparatus 18 may output a two-dimensional image to the display unit 18f of the display unit 13a.
In the two-dimensional image 30 shown in
A method of generating a two-dimensional image using the processing unit 15a will be described next. The following will describe a method of generating a two-dimensional image representing a BRDF as a two-dimensional gradation distribution with a plurality of gradation levels. The processing unit 15a determines maximum and minimum BRDF values obtained based on the detection result (the intensity distribution of reflected light) obtained by the detection unit (sensor 12f). In this case, the processing unit 15a may normalize the BRDF value, obtained based on the detection result (the intensity distribution of reflected light) obtained by the detection unit (sensor 12f), based on the maximum and minimum BRDF values obtained by using a sample surface for calibration. That is, the obtained BRDF value may be normalized based on the maximum and minimum BRDF values respectively obtained as “10” and “0” using the sample surface for calibration.
The processing unit 15a then generates a two-dimensional image representing a BRDF as a two-dimensional gradation distribution based on the set values set by the user via the input unit 14. In this case, the processing unit 15a may generate the two-dimensional image so as to arrange part of the BRDF which corresponds to the specular direction in a central portion of the two-dimensional image. For example, the reflection angle θ′ of specular light is determined by the incident angle θ of light with which the measurement surface 20 is irradiated by the irradiation unit of the measurement unit 12. This makes it possible to generate a two-dimensional image so as to arrange part of a BRDF which corresponds to the specular direction in the central portion as long as an irradiation angle range and a direction angle range are set.
In this case, the set values set by the user include “number of gradation levels”, “range of each gradation level”, “irradiation angle range (for example, ±10°)”, and “direction angle range (for example, ±5°)”. In addition, the processing unit 15a according to this embodiment generates a two-dimensional image so as to arrange part of the obtained BRDF which corresponds to the specular direction in a central portion of the two-dimensional image. However, this is not exhaustive. For example, the processing unit 15a may generate a two-dimensional image so as to arrange the maximum value of the obtained BRDF in a central portion (preferably the center) of the two-dimensional image.
As described above, a measurement system 100 according to this embodiment generates a two-dimensional image, as a two-dimensional gradation distribution, representing the BRDF obtained based on the detection result obtained by the detection unit. The measurement system 100 then outputs the generated two-dimensional image to the display unit 13a (or the display unit 18f). This allows the user to easily and quickly check the reflection tendency of the measurement surface 20 only by giving one glance at the two-dimensional image. Although this embodiment has exemplified the method of generating a two-dimensional image representing a BRDF as a two-dimensional gradation distribution, an image representing a BRDF as a three-dimensional gradation distribution may be generated by a similar method. It is also possible to generate an image representing the intensity distribution of reflected light detected by the detection unit as a two-dimensional gradation distribution by using a similar method.
In a measurement system according to the second embodiment, a processing unit 15a outputs, to a display unit 13a (or causes it to display), the one-dimensional gradation distribution obtained by projecting a two-dimensional gradation distribution in a generated two-dimensional image in a direction set in advance (predetermined direction) based on the two-dimensional gradation distribution. The two-dimensional gradation distribution is projected by integrating a two-dimensional gradation distribution or extracting representative values. For example, the processing unit 15a generates an image representing a one-dimensional distribution in a predetermined direction (to be referred to as a one-dimensional image hereinafter) in the two-dimensional image (the two-dimensional gradation distribution) based on the generated two-dimensional image, and outputs the generated one-dimensional image and two-dimensional image to the display unit 13a. The measurement system according to the second embodiment has the same arrangement as that of the measurement system 100 according to the first embodiment, and hence a description of the arrangement will be omitted.
Likewise, the processing unit 15a generates a maximum value distribution with the ordinate axis representing maximum values and the abscissa axis representing direction angles by obtaining maximum BRDF values at the respective direction angles in the two-dimensional image 30. The processing unit 15a can generate the one-dimensional image 32 representing a maximum value distribution corresponding to direction angles as a gradation distribution by segmenting (gradation processing) the maximum value distribution according to a plurality of gradation levels used to generate the two-dimensional image 30. The output unit 13 outputs, to the display unit 13a, the one-dimensional images 31 and 32 generated by the processing unit 15a so as to make the images adjacent to the two-dimensional image 30. Generating one-dimensional images and outputting them to the display unit 13a in this manner allow the user to easily check part of the two-dimensional image 30 which has a high intensity of reflected light and a specific BRDF shape.
Although this embodiment has exemplified the method of generating one-dimensional images each representing a maximum value distribution in a predetermined direction in a two-dimensional image as a gradation distribution, this is not exhaustive. For example, the integral values of a BRDF in a two-dimensional image may be obtained instead of maximum BRDF values in a two-dimensional image. In this case, the processing unit 15a generates an integral value distribution by obtaining the integral values of a BRDF at the respective irradiation angles (or the respective direction angles) in the two-dimensional image 30 (two-dimensional gradation distribution). The processing unit 15a then generates a one-dimensional image representing an integral value distribution corresponding to irradiation angles (or direction angles) as a gradation distribution. The processing unit 15a may generate a one-dimensional image representing a BRDF distribution on a line crossing the two-dimensional image 30 (two-dimensional gradation distribution) as a gradation distribution instead of the one-dimensional image representing the maximum value distribution or the integral value distribution as a gradation distribution. For example, the processing unit 15a may generate a one-dimensional image representing a BRDF distribution at a predetermined irradiation angle (for example, 60°) as a gradation distribution. In addition, in this embodiment, the output unit 13 outputs the two-dimensional image 30 and the one-dimensional images 31 and 32 to the display unit 13a. However, the output unit 13 may output only the one-dimensional images 31 and 32 to the display unit 13a.
The third embodiment will exemplify a method of causing an information processing apparatus 18 to process a plurality of measurement results obtained by a plurality of times of measurement by a measurement unit 12.
When the user presses a data reception button 41 of the list window 40 via an input unit 18d, the processing unit 18a acquires a plurality of data obtained by a plurality of times of measurement of reflection characteristics by the measurement unit 12 and stored in a storage unit 15b of the control unit 15 from the control unit 15. The processing unit 18a then causes a storage unit 18b to store the plurality of data acquired from the control unit 15. Each data can include a measurement result (index value) on a reflection characteristic of a measurement surface 20 and a two-dimensional image 30 (which may include the one-dimensional images described in the second embodiment) obtained by the control unit 15 (processing unit 15a) of the measurement apparatus 10.
The processing unit 18a then causes the output unit 18c to display a list of a plurality of measurement results in a region 42 of the list window 40 based on a plurality of data stored in the storage unit 18b. In this case, the list window 40 shown in
In this case, when checking the two-dimensional image 30 of a BRDF concerning the selected measurement result, the user further presses (for example, double-clicks) the measurement result on which the selection mark 43 is displayed via the input unit 18d. At this time, as shown in
The present invention can provide a measurement apparatus advantageous in evaluating reflection characteristics of a surface.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-004614 | Jan 2017 | JP | national |
This application is a Continuation of International Patent Application No. PCT/JP2017/042952, filed Nov. 30, 2017, which claims the benefit of Japanese Patent Application No. 2017-004614, filed Jan. 13, 2017, both of which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2017/042952 | Nov 2017 | US |
| Child | 16506197 | US |
