JP6758837B2 - Equipment, methods and programs for acquiring a two-dimensional distribution of gloss mapping - Google Patents

Description

The present invention relates to a technique for measuring the optical properties of an object.

There are objects whose surface appearance changes depending on the illumination direction and observation direction of the light source. This is because the reflected light of the light applied to the surface of the object has different characteristics depending on the illumination direction and the observation direction. Therefore, a technique for measuring the reflection characteristics of such an object is widely known. Patent Document 1 discloses a method of measuring reflected light at a plurality of angles. First, the light receiving portion is scanned within a predetermined area corresponding to the position of the light source, and the position of the specularly reflected light that maximizes the amount of received light is specified. Then, a plurality of measurement positions are determined with reference to the position of the specified specular reflected light, and the reflection characteristics of the object to be measured are measured by moving the light receiving portion to measure the light.

Japanese Unexamined Patent Publication No. 2008-249521

However, according to the method described in Patent Document 1, since a mechanism such as a motor or an arm is required to set the light receiving portion at a plurality of positions, the configuration is complicated.
Therefore, an object of the present invention is to measure the reflection characteristics of an object with a simpler configuration without requiring a mechanism for moving the position of a light source or a light receiving unit.

In order to solve the above problems, the apparatus of the present invention captures an object irradiated with light from a plurality of point light sources whose light amount periodically changes according to periodic functions having different phases at different timings. A sine of pixel values at the same pixel position between the images represented by each image data based on the first acquisition means for acquiring a plurality of image data representing each of the obtained images and the plurality of acquired image data. It is characterized by having a generation means for generating amplitude information representing the amplitude of a wavy change, and a second acquisition means for acquiring a two-dimensional distribution of gloss mapping of the object based on the amplitude information.

According to the present invention, the reflection characteristics of an object can be measured by a simple configuration.

The schematic diagram which shows the appearance of the measuring apparatus of Embodiment 1. FIG. The block diagram which shows the structure of the information processing apparatus of Embodiment 1. The flowchart which shows the process of Embodiment 1. The schematic diagram which shows an example of the illumination image of Embodiment 1. The schematic diagram explaining the relationship between a point light source and a light receiving element. The schematic diagram which shows the relationship between the modulation information of the lighting apparatus of Embodiment 1 and each point light source, and illumination brightness. The schematic diagram explaining the relationship between the illumination light and the reflected light received by a photographing apparatus. The schematic diagram explaining the synthesis of the modulation signal of a different phase. The schematic diagram explaining an example of the measurement object. The schematic diagram which shows an example of a gloss mapping conversion table. The schematic diagram which shows the optical system of the imaging apparatus of Embodiment 1. FIG. The schematic diagram which shows the relationship between the change of the brightness value of a photographed image, and the amplitude information. The schematic diagram explaining the expression of gloss anisotropy by an ellipse. The schematic diagram which shows an example of the illumination image of Embodiment 2. Flowchart showing the process of the second embodiment The schematic diagram explaining the lighting apparatus of the modification 2. The flowchart which shows the detailed procedure of the Tep S301 of the modification 2. The flowchart which shows the detailed procedure of the step S302 of the modification 2. The schematic diagram explaining the schematic structure of the lighting apparatus of the modification 3. The block diagram which shows the functional structure of Embodiment 2. The schematic diagram explaining the structure of the reflected light in a reflection model. The flowchart which shows the calculation procedure of glossy mapping property α in a reflection model. The schematic diagram which shows the appearance of the measuring apparatus of Embodiment 3. The figure which shows an example of the illumination image of Embodiment 3. The schematic diagram which shows the relationship between the change of the brightness value of a photographed image, phase information and bias information. The schematic diagram which shows an example of a specular reflection conversion table. The flowchart which shows the process of Embodiment 3. The flowchart which shows the correction process of the phase information B. The block diagram which shows the functional structure of Embodiment 3.

A mode for carrying out the present invention will be described with reference to the drawings. However, the components described in this embodiment are merely examples, and are not intended to limit the scope of the present invention to them.

[Embodiment 1]
First, the reflection characteristics of an object will be described. FIG. 21 is a schematic diagram illustrating the reflection characteristics of an object. FIG. 21A shows the reflection characteristics when light is irradiated from the direction of the arrow toward the point 1701, and the length of the line segment connecting the point 1701 and the point 1703 on the curve 1702 is from the point 1701 to the point. The intensity distribution of the reflected light reflected in the direction of 1703 is shown. The light reflected on the surface of the object can be separated into a diffuse reflection component shown in FIG. 21B and a specular reflection component shown in FIG. 21C. The diffuse reflection component is a component generated by diffuse reflection of incident light inside the measurement surface, and is observed with uniform intensity in all directions. On the other hand, the specular reflection component is a component related to a glossiness generated by specular reflection of incident light on the surface of the measurement surface, and is observed with an intensity biased in a specific direction. In the following, the reflection direction in which the intensity of the specular reflection component is maximized is referred to as the maximum reflection direction. The intensity of the specular reflection component typically shows a bell-shaped distribution centered on the maximum reflection direction with respect to the reflection direction. ..

FIG. 9 is a schematic view showing an example of a decorative printed matter to be measured in the first embodiment. The decorative printed matter 1001 shown in FIG. 9A is composed of a region 1002 having a small glossy mapping property and a region 1003 (hatched portion) having a large glossy mapping property. Glossy mapability is an index related to the sharpness of the reflected image in a glossy object. When the gloss mapping value of the object is large, the image of the illumination reflected on the object is clearly observed, and conversely, when the gloss mapping value of the object is small, the image of the illumination reflected on the object is blurred. The curve 1004 in FIG. 9B represents the reflection characteristics in the region 1002. Further, the curve 1005 in FIG. 9C represents the reflection characteristic in the region 1003. In any of the reflection characteristics, when light is irradiated from the direction of the point 1007 toward the point 1006, the direction from the point 1006 to the point 1009 becomes the maximum reflection direction. However, in FIGS. 9B and 9C, the distribution shape of the reflected light intensity near the maximum reflection direction is different.

The curve 1005 has a narrower angular range of the specular reflection component than the curve 1004, and the intensity change is steeper with respect to the reflection direction. Therefore, when observed from the maximum reflection direction and the direction in the vicinity thereof, the region 1002 and the region 1003 are observed with different brightness. On the other hand, when observing a direction that does not include a specular reflection component (a direction away from the maximum reflection direction), for example, points 1008 to 1006, the brightness of the area 1002 and the area 1003 match. As a result, the decorative printed matter 1001 looks like a uniform surface or a pattern depending on the observation direction. In this way, the glossy mapping property affects the appearance of the object. In particular, when a printed matter as shown in FIG. 9A is used as a measurement object, the appearance when observed from a specific direction can be grasped by measuring the two-dimensional distribution of gloss mapping. Therefore, in the first embodiment, the two-dimensional distribution of gloss mapping is measured.

Here, the gloss mapping property is a value relating to a change in the intensity of reflected light in the specular reflection direction and its vicinity, and is defined by standards such as JIS K 7374 and ASTM D5767. The index indicating the gloss mapping property output by the measurement system of the present invention is not limited to the value based on the above standard. The value of the feature amount related to the change in the intensity of the reflected light in the direction of specular reflection with respect to the illumination direction and the direction in the vicinity thereof can be used. For example, it may be an angle range in which the reflection intensity is half of the maximum value, or it may be a differential value of the reflection intensity with respect to the reflection direction. In the reflection model of computer graphics (hereinafter also referred to as CG), it is assumed that the surface of the object is composed of a set of minute surfaces, and the normal distribution of the minute surfaces is approximated by a function to express gloss mapping. .. As the function in the normal direction, a normal distribution, a Beckman distribution, a distribution proposed by Forwardbridge-Reitz, or the like is used. The parameters of these distributions can also be regarded as gloss mapping, and the measurement system may be in the form of outputting the parameters of these distributions. Depending on the parameters of the distribution, the magnitude of the parameter value and the magnitude of the gloss mapping property may be opposite, but there is no problem. The gloss mapping property also correlates with the smoothness of the object surface. When the surface of the object is smooth, the glossy mapping property is large, and when the surface of the object is uneven, the glossy mapping property is small. Therefore, the value related to the smoothness of the surface can also be regarded as the gloss mapping property. Therefore, this measurement system can also be used as a device for measuring the smoothness of the surface.

(Outline of measuring device)
FIG. 1 shows the appearance of the measurement system of the present embodiment. The measurement system 100 includes a flat lighting device 11, a photographing device 12, an operation panel 13, and an information processing device 14. In the measurement system of the present embodiment, the photographing device 12 photographs the measured object 15 illuminated by the lighting device 11 based on the user operation using the operation panel 13. The information processing device 14 derives a two-dimensional distribution of gloss mapping property in the measurement object 15 based on a captured image obtained by photographing the photographing device 12. In the following description, the directions of the X, Y, and Z coordinates, and the directions of the azimuth φ and the zenith angle θ related to the illumination direction, the light receiving direction, and the normal direction are defined as shown in FIG. The origin of the X, Y, and Z coordinates is the intersection of the optical axis of the photographing device 12 and the measurement object 15, and the surface of the measurement object 15 is the XY plane.

The illuminating device 11 illuminates the measurement object 15 using a plurality of point light sources arranged on the surface. Each point light source can independently control the brightness value, and emits light with an intermediate brightness as well as turning on and off. In the present embodiment, the lighting device 11 has a flat panel display set corresponding to the object to be measured. In this case, each pixel in the display functions as a point light source by setting the brightness value of each pixel based on the illumination image described later and causing the light to be emitted. The display may be a monochrome display.

The photographing device 12 is a digital camera having a lens that collects light and a sensor that receives light. The lens is a telecentric lens on both sides, and the optical axis direction of the lens related to the light receiving direction is 0 degrees for the azimuth φo and 45 degrees for the zenith angle θo. The lens forms an image of the object 15 on the sensor surface. Since the optical axis of the lens is inclined with respect to the surface of the object to be measured 15, the sensor surface and the lens are installed at positions that satisfy the known Scheimpflug principle. FIG. 11 is a schematic view showing an optical system of a photographing apparatus 12 including a lens and a sensor, which is installed at a position satisfying the principle of Scheimpflug. The light reflected from the surface of the object 15 passes through the main surface 122 of the first lens, the aperture 124, and the main surface 123 of the second lens in this order, and forms an image on the sensor surface 121. The sensor is a two-dimensional sensor such as a CCD or CMOS composed of a light receiving element. Each light receiving element in the sensor converts the amount of received light into an electric signal. As a result, an image composed of pixels having a pixel value proportional to the amount of received light is generated.

Since the first lens and the second range are telecentric lenses, the main ray is changed to the optical axis. The light receiving direction is constant at all measurement points on the measurement object 15. Therefore, each pixel of the image generated by the line s corresponds to one point on the surface of the measurement surface. The number of gradations of the pixel value in the image generated by the sensor is 10 bits, the sensor size is 2/3 inch, and the shooting resolution is 800 dpi in both the X direction and the Y direction. Since the photographing device 12 photographs the object 15 from an oblique direction, the photographing resolution is generally different in the X direction and the Y direction. The resolution conversion process for matching the resolutions in the X direction and the Y direction may be performed immediately after shooting, or may be performed after image processing described later and before outputting the measurement result. Moreover, it does not have to be done.

The operation panel 13 uses a touch panel here. The user of the measurement system sets various measurement conditions and gives an instruction to start measurement via the user interface of the operation panel 13. The operation panel 13 also functions as a display for display, and displays set measurement conditions and measurement results.

The information processing device 14 controls the lighting device 11 and the photographing device 12 based on the user's instruction input via the operation panel 13 to acquire the photographed image of the measurement object 15. In addition, the information processing device 14 performs arithmetic processing described later on the captured image to calculate a two-dimensional distribution of glossy mapping. That is, in the first embodiment, the information processing device 14 functions as a lighting control means, a photographing control means, and an image processing means. The information processing device 14 outputs the processing progress and processing result of the arithmetic processing to the operation panel 13 or an external device (not shown).

(Outline of measurement method)
Here, an outline of a method in which the measurement system 100 in the first embodiment measures the reflection characteristics of the object 15 will be described. FIG. 5 is a diagram showing the relationship between the light source and the reflected light received by the photographing device 12. The pixel P on the sensor of the photographing device 12 receives the reflected light at the position of the measurement point 151 on the measurement object 15. Further, at the measurement point 151, the reflected light received by the pixel P and the illumination light from the point light source Ln have a mirror-finished relationship, and the object 15 is a highly mirror-finished object such as a mirror. In this case, when the intensity of the light emitted from the point light source Ln is modulated as shown in FIG. 5 (b), the brightness value of the pixel P is as shown in FIG. 5 (c) as in FIG. 5 (b). It changes into a sinusoidal shape.

In the first embodiment, the characteristics of the reflected light illuminated from the maximum reflection direction and the direction in the vicinity thereof are measured. Therefore, the lighting device 11 in the first embodiment has a display in which point light sources are arranged at a plurality of positions as shown in FIG. FIG. 6 is a schematic view illustrating the positional relationship between each pixel and the photographing device 12 in the display of the lighting device 11 used as a point light source, and shows an XZ cross section of the measurement system 100. Point light source Lj {j: 1, 2, ... .. 8} Each corresponds to a pixel in the display of the lighting device 11. Each point light source Lj illuminates the measurement point 151 on the object 15 from different directions θj. The reflected light reflected at the measurement point 151 is received by the pixel P in the photographing device 12. For the sake of explanation, the display shows an example of eight pixels in a row. Here, the intensity of each point light source is modulated into a sinusoidal shape having different phases from each other. FIG. 6B is a schematic diagram showing an example of intensity modulation of irradiation light from each point light source L1, L2, L6. The point light sources L1, L2, and L6 all irradiate light modulated in a sinusoidal shape, but the modulation phases are different from each other with reference to the phase of the point light source L1. FIG. 6C shows the relationship between the position of each point light source (the zenith angle indicating the illumination direction) and the phase. The phase of the point light source L1 is 0 degrees. That is, the intensity of the point light source L1 is modulated by K1cosθ + K2. Note that K1 and K2 are constants set according to the intensity (luminance value) that the lighting device 11 can control. Similarly, the phase of the point light source L2 is 45, and the intensity of the point light source L2 is modulated by K1cos (θ-45) + K2. The phase of the point light source L6 is 225 degrees, and the intensity of the point light source L2 is modulated by K1cos (θ-225) + K2.

It is assumed that the photographing device 12 takes a moving image of the measurement object 15 while modulating the intensities of the light sources at each point into sinusoidal shapes having different phases. At this time, the amplitude of modulation of the light receiving intensity of the pixel P in the sensor of the photographing device 12 changes according to the gloss mapping property of the measurement object 15. When the gloss mapping property of the object to be measured is high, the light received by the pixel P is dominated by the reflected light of the light emitted by the specific point light source. FIG. 7 is a schematic view showing the relationship between the illumination light and the reflected light received, and FIG. 7A shows the case of a measured object having a high glossy mapping property. When the gloss mapping property of the measured object is large, the scattering on the surface of the measured object is small, and the light emitted from a specific direction is reflected in a specific direction. In FIG. 7A, it is assumed that the pixel P receives only the reflected light of the irradiation light from the point light source Ln. In this case, all the irradiation light from the light source Ln-1 is reflected in the direction Rn-1, and is not received by the pixel P in the photographing apparatus 12. Therefore, when the gloss mapping property is high, the light intensity received by the pixel P depends only on the point light source Ln as shown in FIG. 5B, and changes linearly according to the change in the irradiation intensity of the point light source Ln. Hereinafter, such a point light source Ln is referred to as a main light source of the pixel P.

On the other hand, when the surface of the object to be measured is uneven and the gloss mapping property is small, the reflected light is scattered in multiple directions. As a result, the pixel P also receives light from a point light source other than the main light source. FIG. 7B shows the relationship between the illumination light and the received reflected light in the measured object having a low gloss mapping property. In FIG. 7B, the illumination light from the light source Ln-1 is reflected not only in the direction Rn-1 but also in the vicinity thereof. Therefore, the pixel P of the photographing device 12 receives the reflected light of the illumination light from the point light source Ln-1 in addition to the reflected light of the illumination light from the point light source Ln. As a result, the reflected light received by the pixel P is a combination of the reflected light of light from different directions. It is assumed that the total reflection intensity (volume) of the specular reflection component is the same even if the gloss mapping property is different. For example, it is assumed that the reflected light received by the pixel P in the measurement of the measurement object having high gloss mapping property according to FIG. 7A is only the light from the point light source Ln, and the light receiving intensity is 1. Further, the reflected light received by the pixel P in the measurement of the measurement object having a small glossy imageability according to FIG. 7B is the light from the point light source Ln (main light source), the point light source Ln-1, and the point light source Ln + 1. The light receiving intensities are 0.8, 0.1, and 0.1 (1 in total), respectively. When the total reflection intensity of the specular reflection components is the same, the smaller the glossy mapping property, the smaller the proportion of the reflected light from the main light source.

FIG. 8 is a schematic diagram showing the relationship between the gloss mapping property of the measured object and the light intensity received by the pixel P, where the horizontal axis shows the time associated with the phase and the vertical axis shows the light intensity. FIG. 8A shows a change in the light receiving intensity when it is assumed that the light intensity of each point light source is modulated by a sine wave having the same phase. The curve 802 shows the intensity change of the reflected light of the light emitted by the point light source Ln in the measurement of the measurement object having a small gloss mapping property according to FIG. 7B. Curve 803 also shows the intensity change of the reflected light of the light irradiated by the point light sources Ln-1 and Ln + 1. Further, the curve 801 shows a change in the intensity of the reflected light of the light emitted by the point light source Ln in the measurement of the measurement object having a large mapping property according to FIG. 7A. The sum of the light intensity of the curve 802 and twice the light intensity of the curve 803 matches the curve 801. That is, the change in the brightness of the pixel P is constant regardless of the gloss mapping property of the measured object. However, in the first embodiment, in order to estimate the glossy mapping property (spread of the specular reflection component), the light intensity of each point light source is modulated into a sinusoidal shape having different phases. 8 (b) and 8 (c) show changes in the light receiving intensity when the light intensity of each point light source is modulated by a sine wave having a different phase. Curves 804, 805, and 806 of FIG. 8 (b) show the reflected light of the light from the point light sources Ln-1, Ln, and Ln + 1, respectively, in the measurement of the measurement object having a small gloss mapping property according to FIG. 7 (b). Shows a change in strength. The curve 807 of FIG. 8C shows the intensity change of the combined light of the reflected light from each point light source shown by the curves 804, 805, and 806. The light receiving intensity (curve 807) when the glossy mapping property is small has a smaller amplitude than the light receiving intensity (curve 801) when the glossy mapping property is large. In this way, when the light intensity of each point light source is modulated in different phases, the amplitude of the change in the brightness of the pixel changes according to the gloss mapping property of the measured object. Therefore, the measurement system in the first embodiment calculates the amplitude of the change in the brightness of the pixel P to estimate the glossy mapping property (spread of the specular reflection component) at the measurement point 151. Thereby, the two-dimensional distribution of the gloss mapping property of the measurement object 15 is derived.

(Configuration of information processing device)
Here, the configuration of the information processing device 14 that controls the lighting device 11 and the photographing device 12 and executes image processing will be described. FIG. 2A shows a hardware configuration of the information processing device 14. The microprocessor (CPU) 201 uses a main memory 202 such as a random access memory (RAM) as a work memory. Further, a program stored in a storage unit 203 such as a hard disk drive (HDD) or a solid state drive (SSD) or a read-only memory (ROM) 204 is executed, and the lighting device 11 and the photographing device 12 are connected via the system bus 205. Control. The storage unit 203 and the ROM 204 store a program for realizing the measurement and various data. An operation panel 13 or a recording medium (computer-readable recording medium) 207 such as a USB memory or a memory card is connected to a general-purpose interface (I / F) 206 such as USB (Universal Serial Bus). The operation panel 13 is also connected to a video card (VC) 208, and the CPU 201 displays a user interface (UI) and information indicating the processing progress and processing result of image processing described later. The lighting device 11 is connected to the system bus 205 via a lighting interface (I / F) 209 such as a video card. The photographing device 12 is connected to the system bus 205 via a camera interface (I / F) 210 such as USB or a camera link. For example, the CPU 201 loads the application program (AP) and various data stored in the ROM 204, the storage unit 203, or the recording medium 207 into a predetermined area of the main memory 202 according to a user instruction input via the operation panel 13. Then, the AP is executed, and the UI is displayed on the operation panel 13 according to the AP. The CPU 201 controls the lighting device 11 and the photographing device 12 according to a user instruction input using the UI to photograph the measurement surface 15, and stores the photographed image data in the main memory 202 or the storage unit 203. Further, the CPU 201 performs a predetermined arithmetic process on the captured image data stored in the main memory 202 according to the AP. Then, the CPU 201 displays the calculation processing result on the operation panel 13 according to the user's instruction, or stores it in the storage unit 203 or the recording medium 207. Further, the CPU 201 transmits / receives programs, data, arithmetic processing results, and intermediate processing data to / from a computer device or server device on a wired or wireless network via a network I / F (not shown) connected to the system bus 205. Can also be done.

(Functional configuration of information processing device 14)
FIG. 2B is a block diagram showing a functional configuration of the information processing apparatus 14 according to the present embodiment. The detailed functional configuration of the information processing apparatus 14 will be described with reference to FIG. 2 (b). The information processing device 14 includes a device control unit 1501, a data storage unit 1502, and a captured image correction unit 1503. The device control unit 1501 transfers the illumination image to the illumination device 11 and causes the display of the illumination device 11 to display the illumination image. Further, the measuring object 15 illuminated based on the illumination image is photographed by the photographing device 12, and the photographed image obtained from the photographing device 12 is stored in the data storage unit 1502. The captured image correction unit 1503 executes a predetermined gradation correction on the captured image stored in the data storage unit 1502.

The amplitude distribution acquisition unit 1504 acquires the amplitude distribution of each pixel in the corrected image based on the corrected image corrected by the captured image correction unit 1503. The amplitude distribution is an image in which the amplitude in the change characteristic of the brightness value in each pixel is stored. This is information for specifying how many point light sources the reflected light from each pixel is combined with the light received by each pixel. The gloss mapping conversion table storage unit 1506 holds a table that converts the amplitude of each pixel into a value for evaluating gloss mapping. The gloss mapping distribution acquisition unit 1505 converts the amplitude of each pixel into gloss mapping based on the amplitude distribution with reference to the gloss mapping conversion table, and derives a two-dimensional distribution of gloss mapping.

The output unit 1507 outputs a two-dimensional distribution with gloss mapping. Alternatively, the captured image or the amplitude distribution which is the intermediate data may be caught.

(About control of lighting device 11)
Next, a lighting image to be displayed on the lighting device 11 will be described. As described above, each point light source (pixel) in the display irradiates light sine-wave-modulated with different phases. When the photographing device 12 measures the measurement object 15 while modulating each point light source in a sinusoidal shape, the brightness value of each pixel in the image generated by the photographing device 12 changes in a sinusoidal shape as in the point light source. The information processing device 14 derives the gloss mapping property of each measurement point from the amplitude of the sine wave in the brightness change of each pixel. In order to calculate the amplitude of the sine wave, three measurement points are required in at least one cycle. In the first embodiment, the measurement is performed four times. FIG. 4 is a diagram illustrating an image for illumination. FIG. 4A shows a display, and the rectangle is a pixel. 4 (b) to 4 (e) show images for illumination. Four illumination images are generated so that each point light source has a modulated brightness for one cycle in four measurements. The information processing device 14 sequentially transmits the lighting images shown in FIGS. 4 (b) to 4 (e) to the lighting device 11. The lighting device 11 controls the brightness value of each pixel of the display based on the received illumination image. The information processing device 14 modulates each pixel (point light source) in the display of the lighting device 11 by switching the illumination image.

The brightness value L of each pixel in the display is represented by the equation (1) because it is modulated in a sinusoidal shape having a certain phase δ (Xd).

L (Xd, Yd, Δi) = K1 × cos (Δi−δ (Xd)) + K2 ... (1)
Here, Xd and Yd are pixel numbers related to the positions in the X-axis direction and the Y-axis direction in the display of the lighting device 11. Further, Δi indicates modulation information, K1 and K2 indicate constants, and δ indicates a phase distribution function related to the initial phase. The constant K1 and the constant K2 are parameters of the contrast and the average brightness of the illumination image, respectively. When the pixel value of each pixel of the illumination image is 8 bits (256 gradations), for example, the constant K1 and the constant K2 are 127. The phase distribution function δ is given by Eq. (2).

δ (Xd) = K3 × Xd ... (2)
Here, K3 is a constant, for example 1, 1. The phase distribution function of the equation (2) means that the phase is determined according to the position in the X direction. The value of the subscript i of the modulation information Δi in the equation (1) indicates the luminance modulation number. When the number of luminance switchings (the number of illumination images) is n, i takes a value from 1 to n. In the present embodiment, n = 4, and the phase for one cycle is divided into four (Δ1, Δ2, Δ3, Δ4) = (0 degree, 90 degree, 180 degree, 270 degree). In FIG. 4, the point light sources arranged in the X direction are set to have different phases from each other, but the directions in which the phases are different are not limited to the X direction. For example, the point light sources may be set to have different phases in the Y direction. In this case, Xd of δ (Xd) in the above equations (1) and (2) is replaced with Yd.

(Measurement procedure)
FIG. 3 is a flowchart showing a measurement procedure executed by the information processing apparatus 14 of the present embodiment. Steps S302 to S309 are realized by reading and executing a program in which the CPU of the information processing device 14 executes the flowchart described below.

First, in step S301, the device control unit 1501 sequentially transfers and displays the lighting images shown in FIGS. 4B to 4E to the lighting device 11. Every time the lighting device 11 illuminates the measurement object 15, the photographing device 12 is made to photograph the measurement object 15. Here, as a result of the measurement, four captured images are acquired. The positional relationship between the lighting device 11, the measuring object 15, and the photographing device 12 is kept constant even when the lighting image is switched. The data storage unit 1502 stores the acquired captured image. The captured image correction unit 1503 executes a predetermined gradation correction for each captured image.

In step S302, the amplitude distribution acquisition unit 1504 calculates the amplitude corresponding to the pixel value of each captured image. First, the amplitude distribution acquisition unit 1504 calculates the change in the brightness value of each pixel in the captured image. FIG. 12 is a diagram showing an example of the result of calculating the change in the brightness value of a certain pixel in the captured image. The horizontal axis is the modulation information of the illumination image corresponding to the shooting timing, and the vertical axis is the brightness value. The amplitude distribution acquisition unit 1504 plots the brightness values of the processing target pixels in the four captured images. Since this measurement result changes in a sine wave shape, the four plot points are approximated to the sine wave in the equation (1). Here, a sine wave that approximates the measurement result is calculated using the following equations (3) to (5).

ss (Xc, Yc) = Σ (Ii (Xc, Yc) × sin (Δi)) ... (3)
sc (Xc, Yc) = Σ (Ii (Xc, Yc) × cos (Δi)) ... (4)
Here, Xc and Yc indicate the pixel number of the captured image. Further, Δi indicates the i-th modulation information, and Ii indicates the brightness value of the captured image when illuminated by the i-th brightness-modulated illumination image. Σ in Eqs. (3) and (4) finds the sum for the subscript i. The value A of the amplitude of the fitted sine wave is calculated as the amplitude information.

A (Xc, Yc) = (ss (Xc, Yc) ^ 2 + sc (Xc, Yc) ^ 2) ^ (1/2) ... (5)
When the amplitude distribution calculation unit 1504 calculates the amplitude information for all the pixels (Xc, Yc), the amplitude distribution calculation unit 1504 outputs an image in which the amplitude information is stored in each pixel as an amplitude distribution.

In step S303, the gloss mapping distribution acquisition unit 1505 acquires a two-dimensional gloss mapping distribution of the measurement object 15 in the amplitude distribution. The two-dimensional distribution of glossy mapping is an image that retains the glossy mapping value S corresponding to each pixel (Xc, Yc) of the captured image. The gloss mapping value S of each pixel is calculated with reference to the gloss mapping conversion table created in advance. FIG. 10 is a schematic view showing an example of a gloss mapping conversion table. As shown in FIG. 10, the gloss mapping conversion table is a table in which the gloss mapping S corresponding to the discrete amplitude information A is described. The gloss mapping value corresponding to the value of arbitrary amplitude information is calculated by using a known interpolation method. Further, the gloss mapping conversion table is created by measuring a measured object having a known gloss mapping property, and is stored in the gloss mapping property conversion table storage unit 1506. As described above, there are various types of indexes representing glossy mapping. More preferably, it is preferable to provide a glossy mapping conversion table corresponding to a plurality of glossy mapping indicators and to switch the glossy mapping conversion table according to a user's instruction. For example, a gloss mapping conversion table that converts the amplitude using the numerical value according to the JIS K 7374 standard as an index of gloss mapping, and a gloss mapping that converts the amplitude using the parameters of the normal distribution of the reflection model as an index of gloss mapping. Prepare a conversion table.

In step S304, the output unit 1507 outputs the two-dimensional distribution of the gloss mapping property of the measurement object 15 obtained in step S303, and ends. The output item may include intermediate processing data such as a captured image and an amplitude distribution.

As described above, in the present embodiment, the plurality of point light sources of the illuminating device 11 are simultaneously modulated into different sinusoidal shapes and simultaneously emitted light to illuminate the object 15 to be measured. The photographing device 12 photographs the measured object 15 a plurality of times in one modulation cycle of each point light source to obtain a captured image. The brightness value of each pixel in the captured image changes in a sinusoidal manner, similar to a point light source. Further, the amplitude of the sine wave in the change in the brightness of each pixel can be associated with the gloss mapping property of the measurement object 15. Therefore, the gloss mapping property of the measurement object 15 is estimated by using the amplitude of the sine wave in the brightness change of each pixel. In particular, in the above-described embodiment, since the light sources having different phases are modulated to emit light at the same time, the time is significantly longer than that of the method of measuring the measurement object 15 each time while emitting light from each point light source in order. Can be shortened. In addition, the change in brightness of each pixel can be detected only by taking pictures at least three times at different timings of the illumination image. As a result, it is possible to reduce the memory capacity for storing captured images and the time required for calculation. In the above description, the case where the phase for one cycle is divided into four times is described as an example, but in the case of three times, the modulation information iΔ is (Δ1, Δ2, Δ3) = (0 degrees, 120 degrees, 240 degrees) should be set. However, the more the lighting image is switched (the number of times of shooting), the more the influence of noise contained in the shot image can be suppressed. Therefore, it is desirable to set the switching (number of times of shooting) of the illumination image in consideration of the measurement accuracy by the user.

A display used as a plurality of point light sources has a high luminance contrast, which is the ratio of the maximum luminance that can be displayed and the initial luminance, a small time variation of the luminance, and a smaller uneven luminance of each pixel in the display. It is desirable that the point light source can be easily identified. Further, it is desirable that the plurality of point light sources are densely arranged and the phase is continuously shifted so that each point light source emits light. Therefore, in the first embodiment, the display is used to illuminate the measurement object 15. When a display is used, the resolution of the display is also the arrangement density of the point light source and is related to the measurement accuracy. Further, it is desirable that the size of the display is designed in consideration of being able to receive a specular reflection component (light reflected from the maximum reflection direction) for all measurement points on the measurement surface 15 measured by the photographing device 12. ..

In the above description, a configuration is described in which the value of the amplitude information is obtained for all the pixels and then the value of the glossy mapping property is obtained. However, the value of the glossy mapping property is calculated for each pixel. Alternatively, it may be configured to calculate the value of gloss mapping property for each n pixels.

[Modification 1]
In the first embodiment, an example in which the value of the amplitude information is calculated by fitting the change in the brightness value of each pixel of the captured image to a trigonometric function has been described, but in the modified example 1, the amplitude is calculated from the maximum brightness value and the minimum brightness value. An example of calculating information will be described. A detailed description of the same configuration as that of the first embodiment will be omitted. In the measurement procedure of the first modification, the process of step S302 is different from that of the first embodiment. In step S302 of the first modification, the amplitude information A of each pixel is calculated by the following equation (6).

A (Xc, Yc) = Max (Ii (Xc, Yc))-Min (Ii (Xc, Yc)) ... (6)
That is, the amplitude information A is the difference between the maximum value and the minimum value of the brightness values Ii taken with different illumination images. Further, the functional configuration of the modified example 1 is different from that of the first embodiment in the amplitude distribution acquisition unit 1504. The amplitude distribution acquisition unit 1504 of the modification 1 acquires the amplitude distribution by performing the process of step S302 of the modification 1 above based on the corrected image corrected by the captured image correction unit 1503. That is, the value of the amplitude information of each pixel of the amplitude distribution is calculated from the brightness value of each pixel of the corrected image by the above equation (6).

In the first modification, the amplitude information is calculated by using the maximum value and the minimum value instead of fitting to the trigonometric function. This eliminates the need for an operation that approximates the brightness change of each pixel of a plurality of captured images to a trigonometric function, and can speed up the processing.

[Modification 2]
In the first embodiment, an example of using a display of a surface light source for the lighting device has been described, but in the second modification, an example of using a line light source will be described. A detailed description of the same configuration as that of the first embodiment will be omitted.

(Lighting device)
FIG. 16 is a schematic view illustrating the lighting device of the second modification. As shown in FIG. 16, the line light source 1801 in which the point light source is arranged in the Xd direction is configured to be movable in the Yd direction. Therefore, in the second modification, the line light source is divided and illuminated while operating in the Yd direction so as to illuminate the same range as the illuminating device 11 of the first embodiment. The arrangement of the line light source is not limited to this example. For example, a line light source in which a point light source is arranged in the Yd direction may be configured to be movable in the Xd direction. Each pixel of the line light source 1801 emits light with the brightness given by the equation (1), as in the first embodiment.

(Measurement procedure)
In the second modification, the processing of step S301 and step S302 is different from that of the first embodiment. FIG. 17 is a flowchart illustrating a detailed procedure of the measurement procedure step S301 in the second modification. First, in step S1901, 0 is set in the constant C that specifies the scanning position of the line light source. Next, in step S1902, the line light source is moved to the position of Yd = C. Next, in step S1903, the illumination images are sequentially displayed on the illumination device 11, and the measurement surface 15 when each illumination image is displayed is photographed by the imaging device 12. The illumination image to be displayed is a line pattern at the position of Yd = C in the illumination image of the first embodiment. Next, in step S1904, it is determined whether or not the imaging at all the scanning positions Yd is completed. When the shooting at all the scanning positions is completed, the process ends. In other cases, the process proceeds to step S1905. In step S1905, the constant C is incremented to set the scanning position Yd of the next line light source, and the process returns to step S1902. By this step, the number of captured images of "the number of illumination images for luminance modulation x the number of scanning positions of the line light source" is acquired.

FIG. 18 is a flowchart showing a detailed procedure of the measurement procedure step S302 in the second modification. First, in step S2001, the amplitude distribution of the measurement surface 15 is acquired. In the second modification, the processing of step S302 of the first embodiment is performed for each scanning position of the line light source, and the amplitude distribution of the number of scanning positions of the line light source is acquired. Next, in step S2002, the maximum amplitude distribution of the measurement surface 15 is acquired. The maximum amplitude distribution is an image in which the pixel values (amplitude information) at the same pixel position of the amplitude distribution group obtained in step S2001 are compared and the maximum amplitude information is selected. In the second modification, this maximum amplitude distribution is used instead of the amplitude distribution of the first embodiment.

(Functional configuration)
In the second modification, the device control unit 1501 and the amplitude distribution acquisition unit 1504 are different from the first embodiment. The device control unit 1501 in the modification 2 performs the process of step S301 of the measurement procedure of the modification 2 described above. That is, at each scanning position of the line light source, each illumination image is displayed on the lighting device 11, and the measurement surface 15 is photographed by the photographing device 12. Then, the number of captured images corresponding to the product of the number of scanning positions of the line light source and the number of illumination images is acquired. The amplitude distribution acquisition unit 1504 in the modified example 2 performs the process of step S302 of the measurement procedure of the modified example 2 described above.

As described above, the measuring device of this modified example uses a line light source having excellent unevenness and luminance stability instead of the surface light source. As a result, the two-dimensional distribution of gloss mapping related to appearance can be acquired with high accuracy.

[Modification 3]
In the first embodiment, an example in which a display of a surface light source is used for the lighting device has been described, but in the third modification, a configuration using a projector and a screen will be described. A detailed description of the same configuration as that of the first embodiment will be omitted.

(Lighting device)
FIG. 19 is a schematic view illustrating the lighting device of the third modification. The lighting device 11 of the modification 3 includes a projector 2101 and a back-illuminated transmissive screen 2102. The screen is not limited to the transmissive type and may be a reflective type. The measurement surface 15 (not shown) is on the opposite side of the projector 2101 with respect to the screen 2102 and is illuminated by the light transmitted through the screen 2102. In this modification, a point on the surface of the screen 2102 is used as a point light source. The points on the surface of the screen 2102 correspond to the pixels of the image input to the projector 2101, and emit light at an arbitrary intermediate level brightness according to the pixel value of the input image. The screen 2102 is installed parallel to the measurement surface 15. Further, in the projector 2101, when the pixel number of the input image is (Xp, Yp), the points on the surface of the screen 2102 corresponding to the pixels having the same Yp value form a straight line, and the direction is the direction of the measuring device. Install so that it is parallel to the X-axis direction. Similarly, the points on the surface of the screen 2102 corresponding to the pixels having the same value of Xp form a straight line, and the points are installed so that the direction is parallel to the Y-axis direction of the measuring device. In this case, the pixel numbers (Xp, Yp) of the image input to the projector 2101 are set as the pixel numbers (Xd, Yd) of the lighting device of the first embodiment, and the two-dimensional distribution of gloss mapping is acquired by the same processing as that of the first embodiment. it can. That is, Xd may be replaced with Xp and Yd may be replaced with Yp in the description of the first embodiment. Alternatively, the coordinate system corresponding to the pixel numbers (Xp, Yp) of the image input to the projector and the X-axis and the Y-axis of the measuring device may be mutually converted by the coordinate conversion. In this case, the pixel number in the coordinate system may be the pixel number (Xd, Yd) of the lighting device of the first embodiment.

As described above, the measuring device of this modified example uses a projector that can be easily increased in size instead of the display. If the screen is installed only during measurement, it is possible to realize a measuring device that is compact and capable of measuring a large size when not in use.

[Embodiment 2]
The second embodiment describes a configuration for measuring a two-dimensional distribution of gloss anisotropy. A detailed description of the same configuration as that of the first embodiment will be omitted.

(Gloss anisotropy)
If the surface of a flat body is also viewed microscopically, it can be regarded as a set of a large number of minute surfaces. When the plane whose normal direction of the minute surface is unevenly distributed in a specific direction is rotated about the normal direction, the amount of light observed changes even if the illumination direction and the light receiving direction are fixed. Such a plane is called a surface exhibiting anisotropic reflection characteristics or a surface exhibiting gloss anisotropy. For example, hairline-processed metal and satin embroidery with a regular texture have a gloss anisotropy. Further, in recent years, in decorative printing, a technique has been proposed in which a fine uneven structure is formed on a surface to develop gloss anisotropy and improve designability. Simple measurement of gloss anisotropy is required for quality control of these reflection characteristics.

(Measurement target)
In the surface exhibiting gloss anisotropy, the variation in the direction of the minute surface normal changes depending on the azimuth angle. Further, the variation in the direction of the minute surface normal corresponds to the glossy mapping property. For example, the value of gloss mapping property based on JIS K 7374 becomes smaller as the variation in the direction of the minute surface normal increases. That is, the value of gloss mapping property of the surface showing gloss anisotropy changes depending on the azimuth angle. Typically, the azimuth with the highest gloss mapping and the azimuth with the lowest gloss mapping are orthogonal to each other, and the gloss mapping changes smoothly in the azimuth between them. Such a characteristic of gloss anisotropy is approximately expressed by a model using an ellipse. According to this ellipse model, the azimuth that maximizes the gloss mapping is the major axis direction of the ellipse, and the value of the gloss mapping in this azimuth is the length of the major axis of the ellipse, the direction orthogonal to the orientation angle. Corresponds the value of gloss mapping of to the length of the minor axis of the ellipse. At this time, the value of the gloss mapping property in the direction of an arbitrary azimuth angle φ is associated with the length of the line segment connecting the two intersections of the above ellipse and the straight line of the azimuth angle φ passing through the center of the ellipse. .. FIG. 13 is a schematic diagram illustrating the expression of gloss anisotropy by the ellipse model. The ellipse 1401 has an azimuth angle of φu at which the gloss mapping property is maximized, and the gloss mapping property value in the azimuth angle direction is αu, and the gloss mapping property value in the direction orthogonal to φu is αv. Represent. The gloss mapping property in the direction of an arbitrary azimuth angle φ is given by a value corresponding to the length of the line segment ab. The measuring instrument of the present embodiment measures the two-dimensional distribution of the parameters of the ellipse model. That is, the two-dimensional distribution of three values, that is, the value of the azimuth angle φu that maximizes the gloss mapping property, the value αu of the gloss mapping property in the direction of the azimuth angle φu, and the value αv of the glossy mapping property in the direction orthogonal to φu. Measure.

(Image for lighting)
Next, the lighting image to be displayed on the lighting device 11 will be described. The illumination image is an image that holds the luminance information modulated in multiple gradations by the periodic function for each pixel, as in the first embodiment, and the luminance L of each pixel is given by the above equation (1). However, in the measurement of gloss anisotropy, unlike the first embodiment, three groups of patterns having different stripe directions are used. Therefore, the phase δ (Xd) depends not only on the Xd direction but also on the Yd direction, and becomes the phase δ (Xd, Yd). As a result, three glossy mapping properties having different azimuth angles are acquired, and from these three glossy mapping properties, the glossy mapping values corresponding to the azimuth angle φu and the lengths of the long axis and the short axis of the ellipse are obtained. .. The directions of the stripes in each group are, for example, a direction orthogonal to the X-axis, a direction parallel to the X-axis, and a direction forming −45 degrees with the X-axis. By illuminating with these striped patterns, glossy mapping properties of 0 degree azimuth, 90 degree azimuth, and 45 degree azimuth are obtained, respectively. Hereinafter, they will be referred to as a first group, a second group, and a third group in this order. The phase division function δ of the illumination image of the first group is given by the above equation (2). The phase distribution functions δ of the illumination images of the second group and the third group are given by the following equations (7) and (8), respectively.

δ (Xd, Yd) = K4 × Yd ... (7)
δ (Xd, Yd) = K5 × (Xd / (2 ^ 0.5) -Yd / (2 ^ 0.5)) ... (8)
Here, K4 and K5 are constants, for example 1. In each group, the minimum number of images for illumination for luminance modulation is 3 patterns, and the gloss anisotropy is measured with a minimum of 9 patterns in total for the 3 groups. FIG. 14 is a schematic diagram showing an example of an illumination image when the number of luminance modulation patterns n = 4. FIG. 14A shows the positional relationship between the lighting device 11 and the lighting image. 14 (b) to 14 (e) are images for illumination of the first group, FIGS. 14 (f) to 14 (i) are images for illumination of the second group, and FIGS. 14 (j) to 14 are shown. (M) shows the illumination image of the third group.

(Measurement procedure)
FIG. 15 is a flowchart showing the measurement procedure of the present embodiment. First, in step S1701, the illumination image of the second embodiment described above is displayed on the illumination device 11, the measurement surface 15 is photographed, and the photographed image is acquired. The positional relationship between the lighting device 11, the measuring surface 15, and the photographing device 12 is kept constant even when the lighting image is switched. Further, the image data captured by the photographing device 12 corrects illumination unevenness and dark current noise of the camera, and corrects the pixel value so that it is proportional to the amount of received light.

Next, in step S1702, the amplitude distribution of the measurement surface 15 is acquired. In the second embodiment, the processing of step S302 of the first embodiment is performed for each group of illumination images, and three amplitude distributions are acquired. Next, in step S1703, the two-dimensional distribution of the gloss mapping property of the measurement surface 15 is acquired. In the second embodiment, the processing of step S303 of the first embodiment is performed for each group of illumination images to acquire three two-dimensional distributions of gloss mapping. The gloss mapping distributions of the first, second, and third groups are gloss mapping distributions having azimuth angles of 0 degrees, 90 degrees, and 45 degrees, respectively.

Next, in step S1704, a two-dimensional distribution of parameters representing gloss anisotropy is acquired. As described above, the parameters representing the gloss anisotropy are the azimuth angle φu that maximizes the gloss mapping property, the gloss mapping property value αu in the azimuth angle φu direction, and the gloss mapping property value in the direction orthogonal to φu. There are three of αv. The values of φu, αu, and αv are given by the following equations (9) to (11).

φu = arctan (P3 / (P1-P2)) / 2 ... (9)
αu = 1 / (((P1 + P2)-((P1-P2) ^ 2 + P3 ^ 2) ^ 0.5) / 2) ^ 0.5 ... (10)
αv = 1 / (((P1 + P2) + ((P1-P2) ^ 2 + P3 ^ 2) ^ 0.5) / 2) ^ 0.5 ... (11)
However, the values of P1, P2, and P3 are based on the following equations (12) to (14).

P1 = -4xS90 ^ 2 / P4 ... (12)
P2 = -4xS0 ^ 2 / P4 ... (13)
P3 = -4x (S0 ^ 2 + S90 ^ 2-2xS45 ^ 2) / P4 ... (14)
However, the value of P4 is based on the following equation (15).

P4 = (S0 ^ 2 + 2 * S0 * S90 + S90 ^ 2-2 x S45 ^ 2) x (S0 ^ 2-2xS0xS90 + S90 ^ 2-2 x S45 ^ 2) ... (15)
Here, S0, S90, and S45 are the values of the gloss mapping property at the azimuth angles of 0 degrees, 90 degrees, and 45 degrees, respectively, and are the values of the pixels of the gloss mapping property distribution acquired in step S1703. For each pixel, the above equations (9) to (11) are calculated to obtain a two-dimensional distribution of φu, αu, and αv.

Next, in step S1705, a gloss anisotropic distribution image is generated. The gloss anisotropy distribution image is a color image representing a two-dimensional distribution of gloss anisotropy, and the color of each pixel is the value of the corresponding pixel in the two-dimensional distribution of φu, αu, and αv obtained in step S1704. Determine based on. For example, the hue angle h and the saturation C * of the colors of the pixels (Xc, Yc) of the gloss anisotropic distribution image are the values calculated by the following equations (16) and (17).

h (Xc, Yc) = φn (Xc, Yc) x2 ... (16)
C * (Xc, Yc) = Kc × (αu (Xc, Yc) -αv (Xc, Yc)) ... (17)
Here, Kc is a constant, and the values of φn (Xc, Yc), αu (Xc, Yc), and αv (Xc, Yc) are the values of the pixels (Xc, Yc) in the two-dimensional distribution of φu, αu, and αv. The value. The value of the lightness L * is set to 50, which is an intermediate value, or the value of the lightness at which the saturation C * is maximized in each hue in the sRGB color gamut. The gloss anisotropic distribution image is preferably a general-purpose color image that retains the sRGB value. This image is generated by calculating the value of sRGB corresponding to the color indicated by the above L *, h, C * by a known method.

Next, in step S1706, various measurement results are output and the process ends. Output items include gloss anisotropy distribution image, two-dimensional distribution of gloss anisotropy parameters φu, αu, and αv, gloss mapping distribution with azimuth angles of 0 degrees, 90 degrees, and 45 degrees, amplitude distribution, and imaging. It may include intermediate data such as images.

(Functional configuration)
FIG. 20 is a block diagram showing a functional configuration of the measuring device 100 according to the present embodiment. The processing performed by the information processing apparatus 14 will be described with reference to FIG. The information processing device 14 includes a device control unit 2201, a data storage unit 2202, and a captured image correction unit 1503. The device control unit 2201 and the captured image correction unit 2203 perform the process of step S1701 of the measurement procedure described above. That is, the device control unit 1701 displays the illumination image of the second embodiment described above on the illumination device 11 and photographs the measurement surface 15 with the imaging device 12. Then, the captured image data is input from the photographing device 12 and stored in the data storage unit 2202. The captured image correction unit 2203 corrects the gradation of the captured image data stored in the data storage unit 2202. Further, the information processing apparatus 14 includes an amplitude distribution acquisition unit 2204, a gloss mapping property distribution acquisition unit 2205, and a gloss mapping property conversion table storage unit 1506. The amplitude distribution acquisition unit 2204 acquires the amplitude distribution by performing the process of step S1702 of the measurement procedure described above based on the corrected image corrected by the captured image correction unit 2203. The gloss mapping distribution acquisition unit 2205 acquires the gloss mapping two-dimensional distribution by performing the process of step S1703 of the above-mentioned measurement procedure based on the amplitude distribution acquired by the amplitude distribution acquisition unit 2204. For details, the gloss mapping conversion table stored in the gloss mapping conversion table storage unit 1506 is referred to, and the value of the amplitude information held by each pixel of the amplitude distribution is converted into the gloss mapping value by a known interpolation method. Convert. Further, the information processing device 14 includes a gloss anisotropy parameter acquisition unit 2206 and a gloss anisotropy distribution image generation unit 2207. The gloss anisotropy parameter acquisition unit 2206 performs the process of step S1704 of the above-mentioned measurement procedure based on the gloss mapping distribution acquired by the gloss mapping distribution acquisition unit 2205, and performs a two-dimensional distribution of parameters representing the gloss anisotropy. To get. The gloss anisotropy distribution image generation unit 2207 performs the process of step S1705 of the above-mentioned measurement procedure based on the two-dimensional distribution of the parameters representing the gloss anisotropy acquired by the gloss anisotropy parameter acquisition unit 2206 to perform the gloss. Generate an anisotropic distribution image. Further, the information processing device 14 includes an output unit 2208. The output unit 2208 performs the process of step S1706 of the measurement procedure described above. That is, based on the user's instruction, the processing results such as the gloss anisotropy distribution image, the two-dimensional distribution of the gloss anisotropy parameters φu, αu, and αv, and other intermediate data are output. In the above description, in the description of each functional configuration, the configuration in which the next processing is performed after the processing of all the pixels is completed and the distribution image is acquired or generated has been described, but the processing is performed for each pixel. It may be configured to process in each of a plurality of pixels.

As described above, according to the measuring device of the present embodiment, it is possible to measure the two-dimensional distribution of gloss anisotropy related to appearance from a minimum of nine captured images. As a result, the appearance of the object can be measured in a short time as compared with the conventional method that requires a larger number of photographs.

[Embodiment 3]
The third embodiment describes a configuration for measuring the parameters of the reflection model related to the SVBRDF (Spatially Varying BRDF), which is a two-dimensional distribution of the BRDF. A detailed description of the same configuration as that of the above embodiment will be omitted. BRDF is a four-dimensional function of the illumination direction ωi (θi, φi) and the observation direction ωo (θo, φo), and when light is incident on the surface of an object from any direction, how much light is reflected in each direction. Indicates whether it will be done. The SVBRDF is a six-dimensional function obtained by adding the positional variable Pxy (X, Y) to the above four variables of BRDF. Due to the large number of dimensions, dense sampling of each variable results in a large amount of data, which takes a long time to measure. Further, SVBRDF is difficult because it is necessary to detect a minute amount of light that is easily affected by noise. On the other hand, many reflection models have been proposed that express the BRDF with a small number of parameters. By measuring the two-dimensional distribution of this parameter, an SVBRDF approximated by the reflection model can be obtained. The measuring device of this embodiment measures the parameters of the reflection model. Once the SVBRDF is obtained, it is possible to predict how the measured object will look when it is illuminated under arbitrary conditions and observed in any direction. As a result, the effects of metallic painting and decorative printing can be confirmed by CG without using actual samples.

Here, the BRDF reflection model calculated by the measurement system of the present embodiment will be described. According to this reflection model, the reflected light observed in an arbitrary lighting condition and observation direction can be estimated by using the parameters measured by this measuring device. In this reflection model, as shown by the following equation (18), the reflected light I is expressed by the sum of the diffuse reflection component Id and the specular reflection component Is.

I = Id + Is ... (18)
FIG. 21 is a schematic diagram illustrating a diffuse reflection component and a specular reflection component. It is assumed that the diffuse reflection component is a component generated by diffuse reflection of incident light inside the measurement surface and is observed with uniform intensity in all directions. In this reflection model using the Lambert model, the diffuse reflection component Id of the reflected light is given by the following equation (19).

Id (X, Y, θi, φi) = Rd (X, Y) × Ein (θi, φi) × cos (θi) ... (19)
Here, Ein is the intensity of the illumination light. Rd is the reflectance of the diffuse reflection component (hereinafter referred to as the diffuse reflectance). For example, it is acquired under the same conditions as the brightness value Id_smp when the measurement surface is illuminated from 0 degrees and received at 45 degrees. It is a ratio with the brightness value Id_std from the reference diffuse reflection surface. Further, the black level is corrected by using the brightness value Id_bk when the illumination is turned off or shaded, and the scaling is performed by using the diffuse reflectance value Cal_Rd045 in the 0 degree illumination 45 degree light reception of the reference diffuse reflection surface. In this case, the diffuse reflectance Rd is given by the following equation (20).

Rd (X, Y) = (Id_smp (X, Y) -Id_bk (X, Y)) / Id_std (X, Y) × Cal_Rd045 ... (20)
As the reference diffuse reflection surface, a pressure-bonded surface of barium sulfate powder or PTFE powder can be used. Also, preferably, the value of Cal_Rd045 uses a value priced by a public measuring institution.

The specular reflection component is a component generated by reflecting incident light on the surface of the measurement surface. A large intensity of the specular reflection component is observed in the specular reflection direction and its vicinity. In this reflection model, which is a modification of the Torrance-Sparrow model, the specular reflection component of the reflected light is given by the following equation (21).

Is (X, Y, θi, φi, θo, φo) = F (X, Y, θi) xD (X, Y, θi, φi, θo, φo) × Ein / cos (θo) ... (21)
Here, Ein is the intensity of the illumination light, F is a function representing Fresnel reflection, and D is a function representing gloss mapping. Fresnel reflection is a phenomenon in which the reflectance changes depending on the direction of incident light or reflected light, and the reflectance increases as the zenith angle approaches 90 degrees. The function F is given by the following equation (22).

F (X, Y, θi, φi) = 1- (1-Rs (X, Y)) × W (θi, φi) ... (22)
Rs is the mirror reflectance measured by this measuring device. This reflectance is the reflectance at the zenith angle θm given by the following equation (23).

θm = arccos (V · Nv) ・ ・ ・ (23)
Here, V is a vector indicating the light receiving direction, and in this measuring device, the zenith angle is 45 degrees and the azimuth angle is 0 degrees. Further, Nv is a vector indicating the optical normal direction measured by this measuring device. The optical normal direction is the direction of the virtual surface normal estimated from the combination of the direction of the incident light and the light receiving direction in which the intensity of the received reflected light is maximum. This definition holds even if the direction of incident light and the direction of light reception are reversed. That is, the optical normal direction is the direction of the virtual surface normal estimated from the combination of the light receiving direction and the direction of the incident light having the highest intensity of the received reflected light. The symbol · indicates the inner product of the vectors, and θm is the angle formed by V and Nv.

Further, W in the above equation (22) is the Fresnel reflection at an angle θv formed by the measured reflectance of Fresnel reflection at the zenith angle θm and the illumination direction ωi (θi, φi) and the optical normal direction Nv. It is a ratio to the reflectance and is given by the following equation (24).

W = (1-cos (θv)) ^ 5 / (1-cos (θm)) ^ 5 ... (24)
Here, θv is based on the following equation (25).

θv = arccos (ωi ・ Nv) ・ ・ ・ (25)
However, ωi is a vector indicating the illumination direction.

D in the above formula (21) represents the normal distribution of the minute surface related to the gloss mapping property. The Torrance-Sparrow reflection model assumes that the surface of an object is composed of a set of microfacets that produce perfect specular reflection, and expresses scattering in each direction based on the distribution of these microfacets in the normal direction. This reflection model uses the distribution model proposed by Trowbridge-Reitz given by the following equation (26) for the function expressing the distribution in the normal direction.

D = (α ^ 2 / (cos (θg) ^ 2 × (α ^ 2-1) +1)) ^ 2 ... (26)
Here, α is a parameter related to the distribution shape and indicates the measured gloss mapping property. α has a value of 1 or less, and the smaller the value, the greater the glossy mapping property. The value of the gloss mapping property α is represented by an elliptical model as in the second embodiment, and the gloss anisotropy is represented. The measuring device of the present embodiment measures the azimuth angle φu that maximizes the gloss mapping property, the gloss mapping property αu in the azimuth angle φu direction, and the gloss mapping property αv in the direction orthogonal to φu. The gloss mapping property α in the illumination direction ωi and the observation direction ωo is calculated using the above parameters φu, αu, and αv. FIG. 23 is a flowchart showing a procedure for calculating the gloss mapping property α. First, in step S2401, the half vector Hv, which is the bisection direction of the vector ωi indicating the illumination direction and the vector ωo indicating the observation direction, is calculated by the following equation (27).

Hv = (ωi + ωo) / | ωi + ωo | ... (27)
Here, | ωi + ωo | represents the magnitude of the vector (ωi + ωo).

Next, in step S2402, the azimuth component φh of the half vector Hv is calculated by the following equation (28).

φh = arctan (Hv_y / Hv_x) ... (28)
However, Hv_x and Hv_y are the X component and the Y component of the vector Hv, respectively.

Next, in step S2403, the gloss mapping property α corresponding to the azimuth angle φh is calculated by the following equation (29).

α = (αwxαv) / (αv ^ 2 × (cos (φh)) ^ 2 + αu ^ 2 × (sin (φh)) ^ 2) ^ 0.5 ... (29)
Θg in the above equation (26) is an angle formed by the half vector Hv and the vector Nv indicating the optical normal direction, and is given by the following equation (30).

θg = arccos (Hv · Nv) ・ ・ ・ (30)
As described above, according to the present reflection model, the intensity of the reflected light observed in an arbitrary illumination direction and the observation direction is obtained from the parameters Rd, Rs, φu, αu, αv and Nv measured by the present measuring device. Can be calculated. Further, the reflected light when illuminated from a plurality of directions can be obtained by adding the reflected light with respect to the light in each illumination direction. Therefore, the reflected light observed under arbitrary lighting conditions can be calculated.

(Configuration of measuring device)
FIG. 23 shows the appearance of the measuring device of this embodiment. The measuring device 2500 includes a lighting device 2501 for measuring the diffuse reflectance in addition to the configuration of the first embodiment. The illuminating device 2501 illuminates the measurement surface with parallel light from the direction of the zenith angle of 0 degrees. As the illumination light source, LEDs, halogens, xenon and the like can be used. A light source having high color rendering properties, brightness, small time variation in brightness, and small in-plane unevenness is preferable. The photographing device 12 has the same configuration as that of the first embodiment. In addition to the measuring surface 15 illuminated by the illuminating device 11, the measuring surface 15 illuminated by the illuminating device 2501 is photographed. When the lighting device 11 illuminates and shoots, the lighting device 2501 turns off or blocks light, and when the lighting device 2501 illuminates and shoots, the lighting device 11 turns off or blocks light. Further, the image is taken even when both the lighting device 11 and the lighting device 2501 are turned off or shaded. In the following, a photographed image taken by illuminating with the lighting device 11 will be referred to as a diffuse reflection photographed image, and a photographed image taken by illuminating with the illumination device 2501 will be referred to as a specular reflection photographed image. Further, the image data taken by turning off or shading both of them is called a black level photographed image. The information processing device 14 of the present embodiment controls the lighting device 2401 in addition to the lighting device 11 and the photographing device 12, and acquires a photographed image of the measurement surface 15. In addition, the information processing device 14 performs arithmetic processing described later on the captured image to calculate the parameters of the reflection model described above. Then, the processing progress and processing result of the arithmetic processing are output to the operation panel 13 or an external device (not shown).

(Image for lighting)
The lighting device 2501 has uniform lighting over the entire surface and does not display a pattern. As the illumination image to be displayed on the illumination device 11, the illumination images of the three groups having different stripe directions used in the second embodiment are used.

(Outline of measurement method)
The diffuse reflectance Rd is calculated by the above formula (20) based on the photographed image of the measurement surface 15 photographed by illuminating with the illumination device 2501. Further, the parameters φu, αu, and αv related to gloss anisotropy are obtained in the same manner as in the second embodiment. However, the value of α in the above equation (26) is used as the value of glossy mapping property. In the gloss mapping conversion table, the value of α corresponding to the discrete amplitude information A is described.

Next, the measurement principle of the optical normal direction Nv will be described. FIG. 24 is a schematic diagram illustrating a measurement principle in the optical normal direction. In FIG. 24 (a), 2601 indicates a point on the surface of the measurement surface 15, and 2602 and 2603 indicate the light receiving direction and the optical normal direction with respect to the point 2601, respectively. Further, 2604 indicates an illumination direction having a specular reflection relationship with the light receiving direction 2602 with respect to the optical normal direction 2603, and 2605 indicates a point light source corresponding to this illumination direction. Further, the pixel of the captured image corresponding to the point 2601 is set to 2606 (not shown). The light receiving direction 2602 is known information determined by the configuration of the measuring device. Further, since the photographing device 12 focuses on the measurement surface 15, the pixels of the photographed image and the points on the surface of the measurement surface 15 have a one-to-one correspondence. Therefore, the XYZ coordinates of the point 2601 can be obtained from the coordinates of the pixel 2606. Here, if the XYZ coordinates (Xill, Yill, Zill) of the point light source 2605 are known, the illumination direction 2604 (Xvi, Yvi, Zvi) from the XYZ coordinates (Xsmp, Ysmp, Zsmp) of the point 2601 is the following equation (31). ) Can be calculated by the formula (33).

Xvi = (Xill-Xsmp) / norm ... (31)
Yvi = (Xill-Xsmp) / norm ... (32)
Zvi = (Zill-Zsmp) / norm ... (33)
However, the norm is based on the following equation (37).

norm = (((Xill-Xsmp) ^ 2 + (Xill-Xsmp) ^ 2 + (Zill-Zsmp) ^ 2) ^ 0.5 ... (34)
At this time, the optical normal direction 2603 (Xvn, Yvn, Zvn) is from the illumination direction 2604 (Xvi, Yvi, Zvi) and the light receiving direction 2602 (Xvc, Yvc, Zvc) to the following equations (35) to (36). ) Is required.

Xvn = (Xvi + Xvc) / (2 × norm) ... (35)
Yvn = (Yvi + Yvc) / (2 × norm) ... (36)
Zvn = (Zvi + Zvc) / (2 × norm) ... (37)
However, the norm is based on the following equation (38).

norm = (((Xvi + Xvc) / 2) ^ 2 + ((Yvi + Yvc) / 2) ^ 2 + ((Zvi + Zvc) / 2) ^ 2) ^ 0.5 ... (38)
This measuring device obtains the XYZ coordinates of the point light source 2605 from the phase information of the brightness change of the pixel 2606. FIG. 25 is a schematic diagram showing changes in the brightness value of the captured image. The horizontal axis of FIG. 25 shows the modulation information of the illumination image, and the vertical axis shows the brightness value of the captured image when the corresponding illumination image is captured. The plot points are the luminance values Ii {i: 1, 2, ... Of the captured image when the number of luminance modulation patterns n = 4. .. n} is shown, and the curve 2701 shows the result of fitting this plot point to the sine wave of the above equation (1). The phase information B is the phase value of the fitted sine wave. The phase information B is given by the following equations (39) to (42).

When 0 ≤ ss and 0 ≤ sc
B = arctan (ss / sc) ... (39)
When 0≤ss and sc <0,
B = arctan (ss / sc) + 180 degrees ... (40)
When ss <0 and sc <0,
B = arctan (ss / sc) + 180 degrees ... (41)
When ss <0 and 0 ≤ sc
B = arctan (ss / sc) + 360 degrees ... (42)
However, the values of ss and sc are based on the following equations (43) and (44).

ss = Σ (Iixsin (Δi)) ... (43)
sc = Σ (Iixcos (Δi)) ・ ・ ・ (44)
Here, Σ is a symbol for obtaining the sum of the subscript i. The value of the phase information B calculated by the equations (39) to (42) is in the range of 0 degrees to 360 degrees, and δ of the equations (2), (7) and (8) is out of this range. If a value is included, the phase information B is corrected as necessary. Details will be described later.

24 (b) to 24 (e) show an image for illumination to be displayed on the illumination device 11, and a position surrounded by a square indicates a point light source 2605. The brightness value of the point light source 2605 changes depending on the illumination image. At this time, the brightness value of the pixel 2606 that receives the specularly reflected light from the point light source 2605 changes in synchronization with the change in the brightness value of the point light source 2605. Therefore, the phase of the brightness change of the pixel 2606 coincides with the phase of the brightness change of the point light source 2605. The illumination images of FIGS. 24 (b) to 24 (e) are patterns in which the phase δ changes in the Xd direction, and the value Bx of the phase information B obtained from the captured image illuminated by this pattern is Xd of the point light source 2605. It corresponds to the phase δx corresponding to the pixel number Xdx in the direction. Therefore, the pixel number Xd'in the Xd direction of the point light source 2605 is obtained from Bx. Similarly, the illumination images of FIGS. 24 (f) to 24 (i) are patterns in which the phase δ changes in the Yd direction, and the value By of the phase information B obtained from the captured image illuminated by this pattern is a point light source. It corresponds to the phase δy corresponding to the pixel number Yd'in the Yd direction of 2605. Therefore, the pixel number Yd'in the Yd direction of the point light source 2605 is obtained from By. If the pixel numbers (Xd', Yd') of the point light source are known, the XYZ coordinates (Xill, Yil, Zill) of the point light source 2605 can be obtained from the configuration of the measuring device.

Next, the measurement principle of the mirror reflectance Rs will be described. In FIG. 25, the bias information C is a bias value when the brightness value of the captured image is fitted to a sine wave. The bias information C is calculated by the following equation (45).

C = Σ (Ii) ... (45)
Here, Σ is the sum of the subscripts i. The bias information C indicates the average value of the reflected light intensity around the specular reflection direction. The reflected light corresponding to the bias information C also includes a diffuse reflection component. The bias information Cs obtained by subtracting the diffuse reflection component is calculated by the following equation (46), where Csmp is the bias information C of the measurement surface, Cstd is the bias information C of the reference diffuse reflection surface, and Rd_smp is the diffuse reflectance Rd of the measurement surface. Given.

Cs = Csmp-Cstd × Rd_smp / Cal_R045 ... (46)
However, Cal_R045 is the reflectance of the reference diffuse reflection surface at 0 degree illumination and 45 degree light reception.

The specular reflection component is distributed around the specular reflection direction based on the normal distribution of the minute surface, and the desired specular reflectance Rs is related to the reflected light in the specular reflection direction, which is the center of the distribution. Here, the distribution shape of the specular reflection component is given by the above-mentioned function D. Therefore, if the function D is integrated for all reflection directions to obtain the average value Dave, the bias information Csd corresponding to the reflected light in the specular reflection direction is obtained from the ratio of this value to the value Ds in the specular reflection direction of the function D. Is given by the following equation (47).

Csd = Cs × Ds / Dave ... (47)
When the function D is given by the above equation (26), the value of Ds is 1. On the other hand, the Dave value depending on the αu and αv values is known by preparing a specular reflection conversion table in which the Dave values corresponding to the discrete αu and αv values are described, and referring to this conversion table. Calculated by the interpolation method of. FIG. 26 shows an example of a specular reflection conversion table. The specular reflection conversion table is prepared in advance based on the above equation (26). The value of the specular reflectance Rs is calculated from the Csd value of the measurement surface, the bias information C value Cstd_s of the reference specular reflection surface, and the Fresnel reflectance value Cal_Rs45 in the 45 degree direction of the reference specular reflection surface by the following equation (48 ).

Rs = Csd / Cstd_s × Cal_Rs45 ... (48)
As the reference specular reflection surface, black polished glass of optical glass BK7 can be used. Preferably, the value of Cal_Rs_45 uses a value priced by a public measuring agency.

(Measurement procedure)
FIG. 27A is a flowchart showing the measurement procedure of the present embodiment. First, the measuring device is calibrated in step S2901. Here, the calibration refers to the process of acquiring the above-mentioned reference plane data and the black level. In this step, the black level photographed image, the diffuse reflection photographed image of the reference diffuse reflection surface, and the bias distribution of the reference diffuse reflection surface and the reference specular reflection surface are acquired. Details will be described later.

Next, in step S2902, the measurement surface is photographed. As described above, in this measuring device, shooting is performed by illuminating with the lighting device 2501 and shooting by displaying the images for illumination of the first group, the second group, and the third group on the lighting device 11. That is, the minimum number of shots required is nine, which is the same as in the second embodiment. In step S2903, the amplitude distribution of the measurement surface is acquired. The amplitude distribution is an image in which the value of the amplitude information A corresponding to each pixel of the captured image is stored. In the third embodiment, the process of step S302 of the first embodiment is performed for each group of the illumination images in the same manner as in the second embodiment, and three amplitude distributions are acquired.

Next, in step S2904, the phase distribution of the measurement surface is acquired. The phase distribution is an image in which the value of the phase information B corresponding to each pixel of the captured image is stored. The captured images taken by displaying the illumination images of the first group and the second group on the lighting device 11 are processed for each group, and two phase distributions are acquired. The phase information B of each pixel is calculated from the above equations (39) to (42) from the luminance value Ii of each pixel of the captured image and the modulation information Δi. In step S2905, the bias distribution of the measurement surface is acquired. The bias distribution is an image in which the value of the bias information C corresponding to each pixel of the captured image is stored. The illumination device 11 displays the illumination image of the first group, processes the captured image, and acquires one bias distribution. The bias information C of each pixel is calculated by the above equation (45) from the brightness value Ii of each pixel of the captured image.

In step S2906, the two-dimensional distribution of the diffuse reflectance Rd is acquired. The value of Rd is calculated by the above formula (20). In the formula (20), Id_smp is the pixel value of the diffuse reflection image acquired in step S2902, and Id_bk and Id_std are the pixel values of the black level photographed image and the diffuse reflection image of the reference diffuse reflection surface acquired in step S2901. In step S2907, a two-dimensional distribution of Nv in the optical normal direction is acquired. The optical normal direction Nv is composed of a zenith angle θn and an azimuth angle φn. The two-dimensional distribution acquired in this step is an image in which the values of θn and φn are stored in each pixel. FIG. 27D is a flowchart illustrating the detailed procedure of step S2907. First, in step S3101, the pixel numbers (Xd, Yd) of the point light source (pixel) of the lighting device 11 whose phase information B of the reflected light matches the phase δ of the illumination light are obtained from the phase distribution obtained in step S2904. The pixel numbers of the point light sources of the lighting device 11 corresponding to each pixel (Xc, Yc) of the captured image are given by the following equations (49) and (50) based on the equations (2) and (7). ..

Xd (Xc, Yc) = B (Xc, Yc) / K3 ... (49)
Yd (Xc, Yc) = B (Xc, Yc) / K4 ... (50)
The pixel numbers (Xd, Yd) of the point light source calculated by the equations (49) and (50) are generally not limited to integers. That is, according to this measuring device, the optical normal direction can be obtained with a resolution higher than the pixel density of the lighting device.

Next, in step S3102, the XYZ coordinates (Xill, Yill, Zill) corresponding to the pixel numbers (Xd, Yd) of the point light source of the lighting device 11 obtained in step S3101 are obtained. The XYZ coordinates (Xill, Yill, Zill) are given by the following equations (51) to (53).

Xill = Kill_11 × Xd + Kill_13 ... (51)
Yill = Kill_22 x Yd + Kill_23 ... (52)
Zill = Kill_33 ... (53)
Here, Kill_11 and Kill_22 are constants related to the pixel size of the lighting device 11, Kill_13 and Kill_23 are constants related to the installation position of the lighting device 11, and Kill_33 is a constant related to the distance between the lighting device 11 and the measurement surface 15.

Next, in step S3103, the XYZ coordinates (Xsmp, Ysmp, Zsmp) of the points on the surface of the measurement surface 15 corresponding to each pixel of the captured image are obtained. The XYZ coordinates (Xsmp, Ysmp, Zsmp) are given by the following equations (54) to (56).

Xsmp = Kcam_11 × Xc + Kcam_13 ... (54)
Ysmp = Kcam_22 × Yc + Kcam_23 ... (55)
Zsmp = 0 ... (56)
Kcam_11 and Kcam_22 are constants related to the resolution of the photographing device 12, and Kcam_13 and Kcam_23 are constants related to the resolution of the photographing device 12 and the number of pixels of the sensor. In step S3104, the illumination direction vector (Xvi, Yvi, Zvi) is obtained. The illumination direction vector is calculated by the above equation (31) to the equation (33). Next, in step S3105, a two-dimensional distribution of Nv in the optical normal direction is acquired. The unit vector (Xvn, Yvn, Zvn) indicating the optical normal direction is derived from the above equation (35) to equation (37) from the illumination direction vector and the light receiving direction vector (Xvc, Yvc, Zvc) obtained in step S3104. ). However, the light receiving direction vectors (Xvc, Yvc, Zvc) having a zenith angle of 45 degrees and an azimuth angle of 0 degrees are given by the following equations (57) to (59).

Xvc = 1 / √2 ... (57)
Yvc = 0 ... (58)
Zvc = 1 / √2 ... (59)
The values of the zenith angle θn and the azimuth angle φn in the glossy normal direction are given by the following equations (60) and (61) from the vectors (Xvn, Yvn, Zvn).

φn = arctan (Yvn / Xvn) ... (60)
θn = arctan (Zvc / ((Xvn ^ 2 + Ync ^ 2) ^ 0.5)) ... (61)
The optical normal direction may be expressed by the X component, the Y component, and the Z component of the vector instead of being expressed by the azimuth angle and the zenith angle. In this case, the two-dimensional distribution in the optical normal direction is an image in which the values of Xvn, Yvn, and Zvn are stored in each pixel. Such image data is used as a normal map which is texture data of computer graphics. In this case, for example, the values of the X component and the Y component (range of -1 to 1) of the vector are associated with 0 to 255 of the R signal and the G signal, respectively, by the following equations (62) to (64). , Z component values (range 0 to 1) correspond to 0 to 255 of the B signal.

R = (Xvn + 1) / 2x255 ... (62)
G = (Yvn + 1) / 2x255 ... (63)
G = Zvnx255 ... (64)
Returning to the description of the measurement procedure of FIG. 27 (a). Next, in step S2908, a two-dimensional distribution of parameters representing gloss anisotropy is acquired. In this step, based on the amplitude distribution obtained in step S2903, the process of step S1703 of the second embodiment is performed to obtain a two-dimensional distribution of φu, αu, and αv.

Next, in step S2909, the two-dimensional distribution of the mirror reflectance Rs is acquired. FIG. 27 (c) is a flowchart illustrating the detailed procedure of step S2909. First, in step S3201, the two-dimensional distribution of the bias information Cs obtained by subtracting the diffuse reflection component is obtained. The value of Cs is calculated by the above formula (46). In the formula (46), Csmp is the pixel value of the bias distribution acquired in step S2905, and Cstd is the pixel value of the bias distribution of the reference diffuse reflection surface acquired in step S2901. Further, Rd_smp is a pixel value of the two-dimensional distribution of the diffuse reflectance Rd acquired in step S2906. In step S3202, the two-dimensional distribution of the average value Dave of all the reflection directions of the function D is obtained. The value of Dave is calculated by a known interpolation method from the pixel values of the two-dimensional distribution of the anisotropic parameters αu and αv acquired in step S2908 with reference to the specular reflection conversion table described above.

In step S3203, the two-dimensional distribution of the bias information Csd corresponding to the reflected light in the specular reflection direction is obtained. The value of Csd is calculated by the above formula (47). In the formula (47), Cs is the pixel value of the two-dimensional distribution of Cs obtained in step S3201, the value of Ds is 1, and Dave is the pixel value of the two-dimensional distribution of Dave obtained in step S3202. In step S3204, the two-dimensional distribution of the mirror reflectance Rs is obtained. The value of Rs is calculated by the above formula (48). In the formula (48), Csd is the pixel value of the two-dimensional distribution of Csd obtained in step S3203, and Cstd_s is the pixel value of the bias distribution of the reference specular reflection surface acquired in step S2901.

Returning to the description of the measurement procedure of FIG. 27 (a). Finally, in step S2910, various measurement results are output and ended based on the user's instruction. Output items include the two-dimensional distribution of the reflection model parameters Rd, Rs, Nv, φu, αu, and αv, the vector V indicating the light receiving direction, the amplitude information distribution, the phase information distribution, the bias information distribution, and the captured image. It may include intermediate data.

Next, the calibration processing procedure of step S2901 will be described. FIG. 27B is a flowchart showing a calibration processing procedure. First, in step S3001, the reference diffuse reflection surface is illuminated by the illumination device 2501 and photographed, and a diffuse reflection photographed image is acquired. In step S3002, the illumination device 11 is displayed with the illumination image of the first group, and the reference diffuse reflection surface is photographed. In step S3003, the illumination device 11 is displayed with the illumination image of the first group, and the reference specular reflection surface is photographed.

In step S3004, both the lighting device 11 and the lighting device 2501 are photographed in a state of being turned off or shielded from light, and a black level photographed image is acquired. In step S3005, the bias distribution of the reference diffuse reflection surface is acquired. The bias distribution is obtained by performing the process of step S2905 described above. In step S3006, the bias distribution of the reference specular reflection surface is acquired. The bias distribution is obtained by performing the process of step S2905 described above. The minimum number of shots required for the calibration process is 1 for taking a diffuse reflection image of the reference specular reflection surface, 3 for taking a first group illumination image, and 3 for the first group illumination image of the reference specular reflection surface. There are a total of eight, three for shooting and one for shooting black-level shot images. That is, according to this measuring device, SVBRDF can be acquired from a minimum of 17 captured images together with the imaging of the measurement surface.

Next, the procedure for correcting the phase information B obtained in step S2904 will be described. As described above, the value of the phase information B calculated by the equations (39) to (42) is in the range of 0 degrees to 360 degrees, which is the remainder obtained by dividing the true phase by 360. Therefore, when δ in the equations (2) and (7) includes a value outside this range, the phase information B is corrected. The principle of correction is as follows. The position POS of the point light source (pixel) of the lighting device 11, which has a relationship between the light receiving direction received by each pixel of the captured image and the specular reflection, changes depending on the optical normal direction. However, the optical normal direction is distributed around the normal direction of the measurement surface. Therefore, it is assumed that the point light source exists around the point light source when the optical normal direction coincides with the normal of the measurement surface. Therefore, 360 degrees to B until the obtained value of the phase information B falls within the range of ± 180 degrees with respect to the phase of the point light source POS when the optical normal direction coincides with the normal of the measurement surface. Is added repeatedly.

FIG. 28 is a flowchart illustrating a procedure for correcting the phase information B. First, in step S3301, the pixel numbers (Xd, Yd) of the point light source POS when the optical normal direction coincides with the normal of the measurement surface are obtained for each pixel of the captured image. The pixel numbers (Xd, Yd) are given by the following equations (65) and (66).

Xd (Xc, Yc) = (Kcam_11 × Xc + Kcam_13-Kill_33-Kill_13) / Kill_11 ... (65)
Yd (Xc, Yc) = (Kcam_22 × Yc + Kcam_23-Kill_23) / Kill_22 ... (66)
Next, in step S3302, the reference phase Ps is obtained by substituting Xd and Yd obtained by the formulas (65) and (66) into the formulas (2) and (7).

Next, in step S3303, the value of B + 180 degrees and the value of Ps are compared. If the former is smaller than the latter, the process proceeds to step S3304, and in other cases, B is output as the corrected phase and the process ends. In step S3304, 360 degrees is added to B to return to step S3303.

(Functional configuration)
FIG. 29 is a block diagram showing a functional configuration of the measuring device 2500 according to the present embodiment. The processing performed by the information processing apparatus 14 will be described with reference to FIG. 29. The information processing device 14 includes a device control unit 3401 and a data storage unit 3402. The device control unit 3401 performs the processes of step S2901 and step S2902 of the measurement procedure. That is, a series of shooting is performed by controlling the lighting device 2501 for diffuse reflection measurement, the lighting device 11 for specular reflection measurement, and the photographing device 12, and the photographed image data is input from the photographing device 12 to store the data. Store in 3402. Further, the information processing apparatus 14 includes a phase information acquisition unit 3403, an amplitude information acquisition unit 3404, a bias information acquisition unit 3405, and a diffuse reflection information acquisition unit 3406. The phase information acquisition unit 3403 acquires the phase distribution by performing the processing of step S2904 of the measurement procedure on the captured image of the measurement surface illuminated by the illumination images of the first group and the second group stored in the data storage unit 3402. To do. The amplitude information acquisition unit 3404 acquires the amplitude distribution by performing the processing of step S2903 of the measurement procedure on the captured image of the measurement surface illuminated by the illumination images of the first group to the third group stored in the data storage unit 3402. To do. The bias information acquisition unit 3405 acquires the bias distribution by performing the processing of step S3005 of the calibration procedure on the captured image of the reference diffuse reflection surface illuminated by the illumination image of the first group stored in the data storage unit 3402. It is stored in the calibration data storage unit 3413. Further, the captured image of the reference specular reflection surface illuminated by the illumination image of the first group stored in the data storage unit 3402 is subjected to the processing of step S3006 of the calibration procedure to acquire the bias distribution, and the calibration data storage unit 3413. Store in. Further, the captured image of the measurement surface illuminated by the illumination image of the first group stored in the data storage unit 3402 is subjected to the processing of step S2905 of the measurement procedure to acquire the bias distribution. The diffuse reflection information acquisition unit 3406 performs the process of step S2906 of the above-mentioned measurement procedure on the captured image of the measurement surface illuminated by the illumination device 2501 stored in the data storage unit 3402 to obtain a two-dimensional distribution of the diffuse reflectance Rd. get. In addition, the information processing device 14 includes an optical normal direction acquisition unit 3407, a gloss anisotropy parameter acquisition unit 3408, and a gloss mapping conversion table storage unit 3411. The optical normal direction acquisition unit 3407 acquires the two-dimensional distribution of the optical normal direction Nv by performing the process of step S2907 of the measurement procedure on the phase distribution acquired by the phase information acquisition unit 3403. The gloss anisotropy parameter acquisition unit 3408 performs the processing of step S2908 of the measurement procedure on the amplitude distribution acquired by the amplitude information acquisition unit 3404 to acquire the two-dimensional distribution of the gloss anisotropy parameters φu, αu, and αv. At this time, the glossy mapping conversion table stored in the glossy mapping conversion table storage unit 3411 is referred to. Further, the information processing device 14 includes a specular reflectance distribution acquisition unit 3409 and a specular reflection conversion table storage unit 3412. The mirror reflectance distribution acquisition unit 3409 uses the following data to perform the process of step S2909 of the measurement procedure to acquire the two-dimensional distribution of the mirror reflectance Rs. The specular reflectance distribution acquisition unit 3409 acquires a two-dimensional distribution of the specular reflectance Rs by using the bias distribution of the reference diffuse reflection surface stored in the calibration data storage unit and the bias distribution of the reference mirror reflection surface. Further, the mirror reflectance distribution acquisition unit 3409 has a two-dimensional distribution of the diffuse reflectance Rd acquired by the diffuse reflectance information acquisition unit 3406 and the gloss anisotropy parameters αu and αv acquired by the gloss anisotropy parameter acquisition unit 3408. The two-dimensional distribution is used to obtain the two-dimensional distribution of the mirror reflectance Rs. Further, the mirror reflectance distribution acquisition unit 3409 acquires a two-dimensional distribution of the mirror reflectance Rs by using the bias distribution of the measurement surface acquired by the bias information acquisition unit 3405. Further, the specular reflectance distribution acquisition unit 3409 refers to the specular reflection conversion table stored in the specular reflection conversion table storage unit 3412 in the process of acquiring the two-dimensional distribution of the specular reflectance Rs. Further, the information processing device 14 includes an output unit 3410. The output unit 3410 performs the process of step S2910 of the measurement procedure. That is, based on the user's instruction, the two-dimensional distribution of the reflection model parameters Rd, Rs, Nv, φu, αu, αv, which is the measurement result, and other intermediate data are output. In the above description, in the description of each functional configuration of 3403 to 3410, the configuration in which the next processing is performed after the processing of all the pixels is completed and the distribution image is acquired has been described, but the processing is performed for each pixel. It may be configured to process each of a plurality of pixels.

As described above, according to the measuring device of the present embodiment, the SVBRD can be acquired from a minimum of 17 captured images.

[Other Embodiments]
In the above embodiment, an example in which the point light source is arranged on a plane or a straight line as the lighting device has been described, but the point light source may be arranged on a curved surface or a curved surface. Further, even when the point light source is arranged on a plane or a straight line, the plane or the straight line does not have to be parallel to the measurement surface. In this case, the degree of freedom in the shape of the lighting device is widened, and the measuring device can be miniaturized. Further, the light source of the lighting device may be monochrome or RGB color. Further, it may be a multi-band color or a spectroscopic light source. When an RGB color, a multi-band color, or a spectroscopic light source illumination device is used, glossy mapping can be obtained for each color. The photographing device may be a monochrome camera or an RGB color camera. Further, it may be a multi-band camera or a spectroscopic camera. When an RGB color camera, a multi-band camera, or a spectroscopic camera is used as in the case of a lighting device, glossy mapping can be obtained for each color. Further, the photographing apparatus is not limited to a two-dimensional sensor such as a CCD or CMOS, and may be equipped with a line sensor. The lens is not limited to a telecentric lens, and does not have to be a lens that satisfies the Scheimpflug condition. For example, a wide-angle lens may be used, the optical axis may be installed so as to be parallel to the normal direction of the measurement surface, and the measurement surface deviated from the center of the optical axis may be imaged on the sensor surface. The illumination image is not limited to the sinusoidal pattern. For example, it may be a triangular wave. Further, the direction of the stripes of the illumination image is not limited to the example of the embodiment, and may be any other direction. Further, the example of outputting the azimuth that maximizes the glossy mapping property as the azimuth angle of anisotropy has been described, but the present invention is not limited to this, and for example, the azimuth angle that minimizes the glossy mapping property may be output. Further, the example in which the feature of gloss anisotropy is represented by the parameters of the ellipse model has been described, but the present invention is not limited to this, and for example, the gloss mapping property of azimuth angles in multiple directions may be used. In this case, for example, if 24 groups of illumination images are used with the stripe directions of the illumination images at intervals of 15 degrees, the gloss mapping property at 24 azimuth angles can be measured. Further, the measuring device may be configured to register the measurement result and the intermediate data of the processing in the server on the Internet via the network I / F.

Further, the present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or a storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit that realizes one or more functions.

Claims (12)

Acquire a plurality of image data representing each image obtained by imaging an object irradiated with light from a plurality of point light sources whose light intensity changes periodically according to periodic functions having different phases from each other at different timings. The first acquisition means to do
Based on the plurality of acquired image data, a generation means for generating amplitude information representing the amplitude of a sinusoidal change in a pixel value at the same pixel position between images represented by each image data,
A second acquisition means for acquiring a two-dimensional distribution of gloss mapping of the object based on the amplitude information,
A device characterized by having. The apparatus according to claim 1, wherein the generation means determines a periodic function that approximates a change in the pixel value, and generates the amplitude information that represents the amplitude of the periodic function. Claim 1 is characterized in that it further includes an illumination control means for irradiating the object with light by controlling a plurality of point light sources that emit light based on a plurality of illumination images modulated by periodic functions having different phases from each other. Or the apparatus according to claim 2. The light source controlled by the illumination control means is a surface light source having a plurality of point light sources on a plane.
The device according to claim 3, wherein the lighting control means switches the plurality of lighting images. The plurality of illumination images are generated so that the brightness value at each pixel position of the image represented by the image data is modulated according to a periodic function, and the plurality of illumination images each have a periodic pattern. The apparatus according to claim 3 or 4. The device according to claim 3, wherein the light source controlled by the lighting control means is a display. The second acquisition means is characterized in that it acquires a two-dimensional distribution of the gloss mapping property of the object based on a table showing a correspondence relationship between the amplitude represented by the amplitude information and the gloss mapping property. The device according to any one of claims 6. Any of claims 1 to 7, further comprising a third acquisition means for acquiring a two-dimensional distribution of parameters representing the gloss anisotropy of the object based on the two-dimensional distribution of gloss mapping. The device according to one item. Based on the two-dimensional distribution of parameters representing the gloss anisotropy of the object, depending on the azimuth at which the gloss reproducibility is maximum or minimum and the azimuth at the azimuth and the azimuth orthogonal to the azimuth. The apparatus according to claim 8, further comprising a fourth acquisition means for acquiring a distribution image of gloss azimuth, which is a color image. The apparatus according to any one of claims 1 to 9, wherein the generation means generates the amplitude information for each pixel position. A program for causing a computer to function as each means of the device according to any one of claims 1 to 10 . Acquire a plurality of image data representing each image obtained by imaging an object irradiated with light from a plurality of point light sources whose light intensity changes periodically according to periodic functions having different phases from each other at different timings. The first acquisition step to do and
Based on the plurality of acquired image data, a generation step of generating amplitude information representing the amplitude of a sinusoidal change in the pixel value at the same pixel position between images represented by each image data, and a generation step.
A second acquisition step of acquiring a two-dimensional distribution of gloss mapping of the object based on the amplitude information, and
A method characterized by having.