Patent Description:
A paint containing a luster material as described above appears to have a different color depending on the observation angle, and thus the paint is widely used as a metallic paint, a pearl paint, or the like for various industrial products such as automobiles requiring designability.

Conventionally, various measuring devices have been proposed in order to regard evaluation of characteristics of such metallic paint or pearl paint as texture other than color.

For example, Patent Literature <NUM> proposes a measurement device in which a line light source is swept in a direction perpendicular to the line light source, a sample surface is imaged by a camera, and sample optical characteristics in the vicinity of specular reflection are evaluated.

In addition, Patent Literature <NUM> proposes, as a device that more easily performs goniometric measurement of reflected light characteristics at a plurality of angles, a device that synchronizes a timing at which an image of a measurement object is captured by an imaging unit with at least one of a timing at which an illumination angle of an illumination unit varies or a timing at which a light receiving angle of the imaging unit varies, and measures a reflectance distribution of the measurement object from an image captured in synchronization with at least one of a variation in the illumination angle or a variation in the light receiving angle. Patent Literature <NUM> discloses a device for detecting flaws on a surface of a flexible object comprising an illuminating means, an image capturing means and an analyzing means that analyzes the images excluding an area with regular reflected light. Patent Literature <NUM> discloses a system that obtains a plurality of sets of images each being acquired using different lighting conditions and combines them into a single image while removing specular highlights. Patent Literature <NUM> discloses a device having a cavity with black inner walls and a sample opening, the device further comprising illumination means for illumination of the cavity and a digital imaging device directed from the cavity to a sample opening. Patent Literature <NUM> discloses a method for evaluating depth feel of painting. Patent Literature <NUM> discloses an apparatus and a method for evaluation of surface properties. Patent Literature <NUM> discloses an image processor comprising specular reflection region detecting portion that detects the position of a specular reflection region based on the data of each pixel that constitutes the image and a rectangular region setting portion that sets an analysis region to become the object of analysis processing in the image based on the position of the specular reflection region. Patent Literature <NUM> discloses an output device for surface features measurement data and surface features measurement device. Patent Literature <NUM> discloses a reflection characteristic-measuring apparatus. Non-Patent Literature <NUM> discloses multispectral systems which are used to image paintings while ignoring areas prone to specular reflections.

However, the technique described in Patent Literature <NUM> is affected by a specular reflection component from a sample surface, and thus has a problem that it is difficult to accurately evaluate optical characteristics when a luster material or the like is included in the surface of the sample. Also in the technique described in Patent Literature <NUM>, elimination of the influence of the specular reflection component from the surface of the measurement object is not considered.

The present invention has been made in view of such a technical background, and an object thereof is to provide an optical characteristics measuring device and an optical characteristics measuring method capable of accurately measuring optical characteristics of a measurement object having a reflecting element such as a luster material included in a painted part on a surface thereof while eliminating an influence of a specular reflection component on a surface of the measurement object of illumination light.

According to a first aspect the present disclosure provides an optical characteristic measuring device in accordance with independent claim <NUM>. According to a second aspect the present disclosure provides an optical characteristics measuring method in accordance with independent claim <NUM>. Further aspects are set forth in the dependent claims, the drawings, and the following description.

The above object is achieved by the following means.

According to the invention, reflected light from a measured site when the measured site of a measurement object is illuminated with illumination light of which an illumination angle is changed to a plurality of illumination angles is received by an imaging element. A specific area at a position where a specular reflection component on a surface of the measured site is not received with respect to any beam of the illumination light having an illumination angle changed in a light receiving area in the imaging element is set as an analysis area, and an optical characteristic of the measured site is analyzed on the basis of a light reception result in the analysis area when the measured site is irradiated with each beam of the illumination light.

That is, in the analysis area of the imaging element, reception of the specular reflection component on the surface of the measured site is avoided, and for each beam of the illumination light having the illumination angle changed, only light directed toward the analysis area, in other words, only specular reflection light derived from a reflecting element among light reflected by the reflecting element such as a luster material of the measured site irradiated with the illumination light is received in the analysis area. Therefore, from the light reception result of the analysis area for each beam of the illumination light having the illumination angle changed, the optical characteristic of the measurement object can be accurately measured while influence of the specular reflection component on the surface of the measurement object is eliminated.

According to the invention, the illumination device is a single illumination display device capable of changing an illumination angle into a plurality of illumination angles by moving a display position of a specific illumination pattern, and a moving direction of the illumination pattern is a direction parallel or perpendicular to a plane formed by a normal of the measured site, a normal of the illumination display device, and a normal of the imaging element, so that the optical characteristic of the measurement object can be measured with a simple configuration.

According to the invention, the analysis area can be easily set by using a two-dimensional imaging element in which an entire light receiving area is larger than a light receiving area of specular reflection light by one beam of illumination light as the imaging element.

According to the invention, when a moving direction when a light receiving position on a side of the imaging element for a specular reflection component on a surface of the measured site sequentially moves in response to a change in the illumination angle of the illumination light is a first direction, the analysis area is set at a position shifted in a direction perpendicular to the first direction, so that the specular reflection component on the surface of the measured site of each beam of the illumination light can be reliably avoided from being received in the analysis area.

According to the item (<NUM>) above, by moving a single bright point or bright line on the single illumination display device, the illumination light of which the illumination angle is changed to a plurality of illuminations angles can be easily achieved.

According to the item (<NUM>) above, a more detailed measurement result can be obtained on the basis of light reception results in the two analysis areas.

According to the item (<NUM>) above, since the exposure time of the illumination light with respect to the imaging element is determined before starting measurement, it is possible to measure the optical characteristic with higher accuracy by an appropriate exposure time.

According to the items (<NUM>) and (<NUM>) above, a more appropriate exposure time can be determined.

According to the items (<NUM>) and (<NUM>) above, since the spatial resolution of the imaging element is <NUM> to <NUM>, it is possible to measure realistic reflection angle characteristics suitable for human eyes.

According to the the item (<NUM>) above, an optical characteristic derived from a luster material contained in the measurement object can be measured.

According to the items (<NUM>) and (<NUM>) above, it is possible to measure optical characteristic including at least one of information on a light distribution characteristic, luminance, a particle diameter, or dispersion aggregation of the luster material.

According to the item (<NUM>) above, the light distribution characteristic is measured in two orthogonal directions.

According to the item (<NUM>) above, an optical characteristic of a measurement object can be measured regardless of the place by carrying the housing.

Hereinafter, the present invention will be described with reference to the drawings.

<FIG> is a block diagram illustrating a configuration of an optical characteristics measuring device according to an example of the present disclosure.

The optical characteristics measuring device illustrated in <FIG> includes a single illumination display device <NUM>, an objective lens <NUM>, a two-dimensional imaging element <NUM> including a CCD sensor or the like, a calculation unit <NUM>, and a measurement result display unit <NUM> including a liquid crystal display device or the like.

The illumination display device <NUM> displays at least one illumination pattern, and irradiates a measured site 100a of the measurement object (also simply referred to as a sample) <NUM> with illumination light L1 from the displayed illumination pattern.

The imaging element <NUM> includes a large number of pixels, receives reflected light L2 from the sample <NUM> on each pixel via the objective lens <NUM>, converts the reflected light L2 into image data, and outputs the image data.

The illumination display device <NUM> and the imaging element <NUM> are arranged in a positional relationship in which the imaging element <NUM> can receive reflected light of a specular reflection component that is specular reflection on the surface of the measured site 100a. That is, the illumination display device <NUM> and the imaging element <NUM> are arranged in a relationship such that the angle formed by a normal of the measured site 100a of the sample <NUM> and a normal of the illumination display device <NUM> and the angle formed by the normal of the measured site 100a of the sample <NUM> and the imaging element <NUM> are equivalent.

The image data that is an electrical signal output from the imaging element <NUM> is converted as necessary into a digital signal through an IV conversion circuit and an AD conversion circuit that are not illustrated, and is sent to the calculation unit (corresponding to the analysis unit) <NUM>. The calculation unit <NUM> uses the sent image data to perform calculation processing of optical characteristics of the measured site 100a, for example, optical characteristics derived from a luster material by the CPU or the like, and the measurement result display unit <NUM> displays the calculation result, that is, the measurement result by the calculation unit <NUM>. Note that conversion of the image data output from the imaging element <NUM> into the digital signal may be performed by the calculation unit <NUM>.

The calculation unit <NUM> may be a dedicated device or may be constituted by a personal computer. Further, the image data output from the imaging element <NUM> and processed into the digital signal may be sent to the calculation unit <NUM> via a network. In this case, even if the calculation unit <NUM> is present at a place away from the measurement place, the optical characteristics can be measured.

Next, spatial resolution of the imaging element <NUM> will be described. In order to detect a phenomenon visually observed by the imaging element <NUM>, the imaging element <NUM> needs spatial resolution corresponding to human eyes. According to one study, the minimum width that can be distinguished by the human eye is said to be about <NUM> minutes. Assuming that the distance from the pupil to the observation object is <NUM> to <NUM>, the distance between the two distinguishable points is calculated to be <NUM> to <NUM>.

Further, when the measurement object is a painted surface containing a luster material of an automobile exterior material, the particle size of the luster material contained in the paint film is about <NUM> to <NUM> for a small one and about <NUM> for a large one. It is more desirable that the imaging element <NUM> can spatially distinguish each of the luster materials.

From the above, the spatial resolution of the imaging element <NUM> is desirably about <NUM> to <NUM>.

<FIG> is a perspective view illustrating an appearance of the optical characteristics measuring device according to an example of the present disclosure. Here, the optical characteristics measuring device is configured to be a portable handy type.

Specifically, the illumination display device <NUM>, the objective lens <NUM>, the imaging element <NUM>, and the calculation unit <NUM> are accommodated in a housing <NUM>. Further, on an upper surface of the housing <NUM>, a portable grip portion <NUM> is provided, and the measurement result display unit <NUM> for displaying a measurement result is provided, and moreover, on a lower surface of the housing <NUM>, an opening <NUM> for irradiating the measured site 100a of the sample <NUM> with illumination light and taking in reflected light from the measured site is formed.

When the optical characteristics measuring device illustrated in <FIG> is used, the grip portion <NUM> is gripped, and the opening <NUM> on the lower surface is positioned at the measured site 100a of the sample <NUM>. In this state, the sample <NUM> is irradiated with illumination light from the illumination display device <NUM> accommodated in the housing <NUM>, the reflected light is received by the imaging element <NUM>, optical characteristics are measured by calculation by the calculation unit <NUM> using the image data output from the imaging element <NUM>, and the measurement result is displayed on the measurement result display unit <NUM>.

With such an optical characteristics measuring device, the optical characteristics can be measured regardless of the place by carrying the housing.

Next, measurement of specific optical characteristics will be described.

The optical characteristics are characteristics that the measured site 100a reflects the illumination light L1 at what reflection angle, and are evaluated in a specific analysis area of the entire light receiving area of the imaging element <NUM> as described later. Here, a case where the optical characteristic is information (for example, a light distribution angle) related to the light distribution of the luster material will be described.

As illustrated in <FIG>, in a typical layer structure of an automobile surface on which a paint including a luster material is applied, a luster material containing layer <NUM> containing a luster material <NUM> is applied and laminated on a base layer <NUM> as a base material, and a clear layer <NUM> formed of a clear coat layer or the like is further laminated thereon. An optical model for measuring optical characteristics of such a layer structure will be considered.

The luster material <NUM> in a paint film exists with a certain inclination (orientation). The orientation distribution generally has a peak in the horizontal direction (zero degrees) of the paint film surface, and has a distribution in which the number of luster materials decreases with an increase in angle.

It is said that the state of the orientation depends on painting conditions such as blowing speed, pressure, and film thickness of the paint as well as design factors such as the luster material <NUM> and the type of the paint.

When the illumination light L1 is incident on the measured site 100a of the sample <NUM> having such a luster material containing layer <NUM>, a part thereof is specularly reflected (specular reflection) at the surface of the clear layer <NUM>, and a part thereof is transmitted through the surface of the clear layer <NUM>. A part of the transmitted light is specularly reflected (specular reflection light L12) by the luster material <NUM> inside the paint.

The luster material reflection reflects light in a direction corresponding to the inclination of the luster material <NUM> from the horizontal direction of the paint film surface. Usually, orientation angles θ of many of the luster materials <NUM> fall within <NUM>° with respect to the sample normal direction. When the refractive index of the clear layer is n = <NUM> and the incident angle is <NUM>°, this corresponds to |θas| ≤ <NUM>° when expressed by an as angle in <FIG>.

A case where the optical characteristics of the measured site 100a of the sample <NUM> including the luster material containing layer <NUM> and the clear layer <NUM> are measured by the optical characteristics measuring device according to the present example will be described.

It is assumed that the resolution on the sample surface is selected to be sufficiently high, and there is spatial resolution enough to capture bright spots derived from each luster material in the automobile exterior paint. As described above, the spatial resolution of the imaging element <NUM> is desirably about <NUM> to <NUM>.

The illumination display device <NUM> displays a predetermined illumination pattern and moves the displayed illumination pattern in one direction. As an example of the illumination pattern, a single bright point can be mentioned. A state in which the single bright point is displayed and moved on the illumination display device <NUM> is illustrated in <FIG>, and a captured image acquired by the imaging element <NUM> when the bright point is moved is illustrated in <FIG>. In this example, the moving direction of the bright point <NUM> is a direction parallel to a plane constituted by the normal of the measured site 100a, the normal of the illumination display device <NUM>, and the normal of the imaging element <NUM> (horizontal direction in <FIG>).

In <FIG>, a rectangular white portion is a bright point <NUM>, and a black portion is a non-light emitting region. The illumination display device <NUM> has a rectangular display surface, and in the screen number A1, a bright point <NUM> is displayed at an intermediate portion in a vertical direction of one end portion (left end portion in <FIG>) in a horizontal direction of the display surface. As indicated by arrow H1 on screen A1, bright point <NUM> sequentially moves (scans) to the other end side (right end side in <FIG>) in the horizontal direction of the display surface. The screen numbers A1 → A2 →. indicate the display surfaces on which the bright point <NUM> is moving.

On the other hand, as illustrated in <FIG>, the two-dimensional imaging element <NUM> has a rectangular light receiving area as a whole including a large number of pixels. The image number B1 indicates a captured image of the imaging element <NUM> when illuminated on the display screen of the screen number A1, and a white point indicates that the luminance is high in the light receiving portion <NUM> at the intermediate portion in the vertical direction at one end portion in the horizontal direction (left end portion in <FIG>) in the entire rectangular light receiving area. The reason why the luminance of the light receiving portion <NUM> is high is that the specular reflection component specularly reflected by the surface of the clear layer <NUM> when the illumination light from the bright point <NUM> indicated by the screen number A1 is applied to the measured site 100a is received. That is, the light receiving portion <NUM> is the arrival point of the specular reflection component specularly reflected by the surface of the clear layer <NUM> to the image element <NUM>.

When the bright point <NUM> of the illumination display device <NUM> moves (scans) as indicated by the screen number A2 →. , the illumination angle with respect to the measured site 100a sequentially changes, but the angle of the imaging element <NUM> on the light receiving side is fixed. From the position of the bright point <NUM> and the geometry of the imaging element <NUM>, the incident light direction and the emitted light direction at each measured site 100a can be uniquely specified.

Therefore, the position of the light receiving portion <NUM> that receives the specular reflection component on the surface of the clear layer <NUM> when the measured site 100a is irradiated with the illumination light from the moved bright point <NUM> also sequentially moves as indicated by the image numbers B2 →. to the other end side (right end side of <FIG>) in the horizontal direction.

Here, a specific example of the changeable illumination angle range of the illumination display device <NUM> will be supplemented. For example, as illustrated in <FIG>, when the distance between the illumination display device <NUM> and the measured site 100a of the measurement object <NUM> is <NUM>, the illumination display device <NUM> is <NUM> inches QVGA, and the length of the long side is <NUM>, the illumination angle of the bright point <NUM> can be achieved up to <NUM>° at the as angle. As described above, the illumination angle width is sufficient for evaluating the luster material <NUM>.

For the luster material <NUM> included in the luster material containing layer <NUM>, in a case where the illumination angle and the light receiving angle are equal to each other with respect to the plane normal of the luster material <NUM>, the imaging element <NUM> receives specular reflection light of the luster material <NUM>, and the obtained luminance is maximized. On the other hand, since the reflection luminance decreases as deviating from the relationship of specular reflection, when the bright point <NUM> is moved, a distribution having a luminance peak in a certain specific pattern (= specific illumination angle) is obtained.

This state is illustrated in <FIG>. These drawings schematically illustrate a state of reflection from the luster material <NUM> when the bright point <NUM> of the illumination display device <NUM> is moved in a width direction of the display surface. Further, each of the drawings on the lower side illustrates the luster material of interest <NUM> interposed between + marks and + marks.

In <FIG>, the bright point <NUM> does not move, the illumination angle with respect to the measured site 100a is θ1, and in this state, the luminance of the luster material <NUM> inclined downward to the right becomes maximum as illustrated at the luster material of interest <NUM>. In <FIG>, the bright point <NUM> moves and the illumination angle with respect to the measured site 100a is θ2, and in this state, the luminance of the luster material <NUM> arranged substantially horizontally becomes maximum as illustrated at the luster material of interest <NUM>. In <FIG>, the bright point <NUM> further moves and the illumination angle with respect to the measured site 100a is <NUM>, and in this state, the luminance of the luster material <NUM> inclined downward to the left becomes maximum as illustrated at the luster material of interest <NUM>. In <FIG>, the bright point <NUM> further moves and the illumination angle with respect to the measured site 100a is θ4, and in this state, the luminance of the luster material <NUM> further inclined downward to the left becomes maximum as illustrated at the luster material of interest <NUM>.

As described above, the angle at which the luminance is maximized differs for each pixel, and depends on the reflection angle of the luster material <NUM> and thus the orientation angle. In other words, it is possible to estimate the orientation angle of each of the luster materials from the peak position of the luminance.

However, as described above, in a case where the specular reflection component on the surface of the clear layer <NUM> is included, the peak of the luminance value appears at a position different from the position derived from the luster material, and thus it becomes difficult to estimate the optical characteristics derived from the luster material.

Therefore, in this example, a specific area that does not receive the specular reflection component on the surface of the clear layer <NUM> in the light receiving area of the imaging element <NUM> is set as an analysis area, and the optical characteristics of the luster material <NUM> are analyzed on the basis of a light reception result in the analysis area.

Describing this analysis area, as in the image number B1 of <FIG>, a rectangular area <NUM> indicated by a dashed line and a rectangular area <NUM> indicated by a solid line are provisionally set in the entire light receiving area of the imaging element <NUM>. As described above, the position of the light receiving portion <NUM> that receives the specular reflection component on the surface of the clear layer <NUM>, in other words, the position where the specular reflection component on the surface of the clear layer <NUM> reaches the imaging element <NUM> side also moves in the horizontal direction corresponding to the movement of the bright point <NUM> of the illumination display device <NUM> in the horizontal direction, but the dashed-line rectangular area <NUM> is located on a line in the moving direction (corresponding to the first direction) of the light receiving portion <NUM>, and the specular reflection component on the surface of the clear layer <NUM> is received depending on the position of the bright point <NUM>. On the other hand, the solid-line rectangular area <NUM> is at a position shifted in a perpendicular direction from the moving direction of the light receiving portion <NUM> accompanying the movement of the bright point <NUM>, and does not receive any specular reflection component on the surface of the clear layer <NUM> by each bright point <NUM> even if the bright point <NUM> moves.

Accordingly, the solid-line rectangular area <NUM> that receives only specular reflection light derived from the luster material and does not receive a specular reflection component on the surface of the clear layer <NUM> is set as an analysis area, and a light reception result of pixels in the analysis area <NUM> is analyzed to obtain optical characteristics of the luster material <NUM>.

A specific example will be described. As illustrated in <FIG>, when the bright point <NUM> is moved <NUM> times from the left to the right to change the illumination angle <NUM> times and <NUM> images captured at each position of the bright point <NUM> are set as images (image-number) <NUM> to <NUM>, examples of luminance values obtained for each of the <NUM> images for one pixel each in the solid-line rectangular area (analysis area) <NUM> and the dashed-line rectangular area <NUM> are illustrated in <FIG>. An upper graph in the drawings is a pixel value for a pixel in the dashed-line rectangular area <NUM>, a lower graph is a pixel value for a pixel (pixel of interest) in the solid-line rectangular area <NUM>, the horizontal axis of each graph is an image number, and the vertical axis is a luminance value. The luminance value is held in eight bits, the maximum value is <NUM>, and the minimum value is <NUM>.

Further, <FIG> illustrate cases where peaks of specular reflection light of the luster material <NUM> exist in the first half image, the image near the center, and the second half image, respectively.

In the upper graph, a peak always exists near the image number <NUM> in any of 7A to 7C. This is a peak of the specular reflection component on the surface of the clear layer <NUM>. Because of the presence of this peak, it is difficult to directly associate the peak position with the orientation of the luster material <NUM>. In particular, a luminance component derived from the luster material having a peak near the image number <NUM> is buried in the specular reflection component on the surface of the clear layer <NUM> as in the upper graph of <FIG>, and thus it is difficult to detect the peak of the luminance component derived from the luster material. Further, the luster material reflection exhibiting a peak at this position is caused by the luster material <NUM> having a small inclination, and there are usually many such reflections from the orientation distribution of the luster material <NUM>.

On the other hand, in the lower graph, such a peak structure is not observed, and only the peak derived from the luster material reflection is observed regardless of the peak position in any position of 7A, 7B, and 7C. Therefore, the orientation information of the luster material <NUM> can be calculated from the peak position. That is, highly accurate light distribution information can be calculated on the basis of luminance value of the pixels in the solid-line rectangular area (analysis area) <NUM>.

The calculated orientation information will be described.

As illustrated in <FIG>, it is assumed that the horizontal direction of the measured site 100a is an x direction, the vertical direction is a y direction, the inclination in the y direction with the x direction of the luster material <NUM> as the central axis is θx, the inclination in the x direction with the y direction as the central axis is θy, and the bright point <NUM> of the illumination display device <NUM> is moved in the x direction. θx = θy = <NUM> in the normal direction of the measured site 100a.

The orientation information of the luster material <NUM> obtained by the measurement method of the present example corresponds to θx = θx' and θy = θy'. Here, θx' is an angle uniquely determined from a shift amount of a moving direction line of the analysis area <NUM> where the specular reflection light by the luster material <NUM> of the moving bright point <NUM> is analyzed and the geometry of the imaging element <NUM>. On the other hand, θy' corresponds to the peak position obtained by the above measurement.

In many cases, an automobile exterior or the like has a surface structure as illustrated in <FIG> and the illumination light incident on the measured site 100a of the measurement object <NUM> is refracted on the surface of the clear layer <NUM>, and thus it is possible to calculate accurate orientation information of the luster material <NUM> from the above information by taking the effect into account.

Further, since the peak of the luminance value obtained in the analysis area <NUM> does not include the specular reflection component on the surface of the clear layer <NUM> and is derived purely from the reflection of the luster material <NUM>, the luminance information of the luster material <NUM> can be calculated from the acquired peak value.

Note that, in the analysis area <NUM>, the specular reflection component by the clear layer <NUM> is not included even in the pixels other than the pixel of interest, and thus statistical information such as luminance distribution and orientation distribution can also be acquired by performing similar analysis on all the analysis areas.

Further, since the position vertically shifted from the moving direction line of the light receiving portion <NUM> for the specular reflection component by the clear layer <NUM> is analyzed, it is possible to acquire the orientation distribution regarding θy includingθy = <NUM> with respect to the luster material <NUM> of a certain θx = θx'.

As described above, the measured site 100a of the measurement object <NUM> is illuminated with the illumination light of which the illumination angle is changed to a plurality of illumination angles by moving and scanning the bright point <NUM> in one direction, a specific area that does not receive any specular reflection component on the surface of the clear layer <NUM> of each illumination light in which the illumination angle is changed in the light receiving area in the imaging element <NUM> is set as the analysis area <NUM>, and the optical characteristics of the luster material <NUM> are analyzed on the basis of a light reception result of only the specular reflection light by the luster material <NUM> in the analysis area <NUM>. Thus, the optical characteristics such as luminance and light distribution characteristic of the luster material <NUM> can be accurately measured while eliminating the influence of the specular reflection component on the surface of the clear layer <NUM>.

Note that the optical characteristics that can be obtained are not only luminance and orientation information. By analyzing two-dimensional spatial luminance distribution, it is also possible to quantify the magnitude of a particle diameter of a contained luster material <NUM> and the dispersion and aggregation of the luster material.

For example, <FIG> illustrates a case where a large number of luster materials <NUM> having a small particle diameter are present, and <FIG> illustrates a case where a large number of luster materials <NUM> having a large particle diameter are present. The particle diameter of a luster material <NUM> can be calculated from the fact that the light distribution angle and the length in the horizontal direction of the luster material <NUM> are recognized by analyzing a two-dimensional spatial luminance distribution.

Further, similarly, by analyzing the two-dimensional spatial luminance distribution, the presence or absence of unevenness (whether particles are uniformly dispersed or there is an aggregated location) of the luster material for each location can also be quantified. <FIG> illustrates a state in which the luster materials are dispersed, and <FIG> illustrates a state in which the luster materials <NUM> are aggregated.

By analyzing and evaluating the optical characteristics in this manner, it is possible to measure a lot of information on paint physical properties represented by at least one of luminance/chromaticity, orientation, particle size, dispersion aggregation, and the like of the luster material <NUM>.

Further, since the single illumination display device <NUM> is used, it is possible to suppress complication of the entire configuration of the optical characteristics measuring device as compared with the case of using a plurality of light sources.

In addition, the moving direction of the bright point <NUM> may be set to the vertical direction in <FIG>, that is, a direction perpendicular to a plane constituted by the normal of the measured site 100a, the normal of the illumination display device <NUM>, and the normal of the imaging element <NUM>.

In this example, how to determine the exposure time in the analysis area <NUM> will be described.

Since the optical characteristics differ depending on the measurement object <NUM>, the appropriate exposure time differs for each measurement object <NUM>. From the viewpoint of shortening the entire measurement time, it is desirable to first perform preliminary measurement for determining the exposure time, and then perform a series of main measurement with an optimum exposure time calculated using acquired information.

It is desirable that the exposure time is long from the viewpoint of the signal-to-noise ratio (S/N), but it is necessary not to exceed the measurement maximum luminance value from the viewpoint of luminance value calculation and luminance change analysis. Accordingly, it is desirable to select an exposure time during which the luminance value of the bright spot of the luster material <NUM> when the illumination light is specularly reflected falls within a desired luminance range.

A process of determining such an exposure time will be described.

The analysis area <NUM> actually used in the present measurement is used, and the illumination pattern (for example, bright point) actually used in the present measurement is used. It is desirable that the illumination pattern illuminates a location close to the analysis area <NUM>, but is not limited thereto.

As illustrated in <FIG>, an image is captured in a preset short time t1 using the illumination pattern. Among the captured luminance images in the analysis area <NUM>, luminance values of characteristically bright ones are used as illustrated in <FIG>. The characteristically bright one may use the one having the highest luminance value in the analysis area <NUM>, but is not limited thereto.

In general, since there is a linear relationship between the exposure time and the acquired luminance value, when the luminance value at a certain exposure time is measured, it is possible to calculate the exposure time that falls within a desired luminance range. Accordingly, as illustrated in <FIG>, t2, which is an exposure time suitable for the illumination image, is calculated using the linearity.

In the main measurement after the preliminary measurement, the exposure time t2 is used as a reference, and the measurement is performed at an exposure time suitable for each illumination.

Such determination of the exposure time t2 is desirably performed for each movement of the illumination pattern, in other words, for each illumination angle of the illumination light, but is not limited thereto.

In the second embodiment, since the exposure time for the imaging element <NUM> is determined for each illumination angle of the illumination light before starting the main measurement as described above, it is possible to measure the optical characteristics with higher accuracy with an appropriate exposure time.

As illustrated in <FIG>, the analysis areas <NUM> and <NUM> in the imaging element <NUM> are set at positions shifted in perpendicular directions V2 and V3 with respect to a moving direction H on both sides of the moving direction H of the light receiving portion <NUM> for the specular reflection component on the surface of the clear layer <NUM>. Conversely, the light receiving portion <NUM> passes through the midpoint between the analysis areas <NUM> and <NUM>. The positions of both the analysis areas <NUM> and <NUM> may not be the same in each captured image when the bright point <NUM> is moved.

In many cases, the distribution of the luster material <NUM> depends only on the angle between the normal of the luster material <NUM> and the normal direction of the measured site 100a. Thus, an orientation distribution related to θy including θy = <NUM> with respect to the luster material <NUM> of θx = θx' coincides with an orientation distribution related to θy includingθy = <NUM> with respect to the luster material <NUM> of θx = -θx'.

By using such properties and setting the analysis areas <NUM> and <NUM> on both sides in the moving direction H2 of the light receiving portion <NUM> with respect to the bright point <NUM>, the analysis range can be increased in a state where the light receiving angle width is suppressed, and observation of more luster materials can be performed at a time.

Note that, if the analysis area <NUM> is made large, the illumination/light receiving angle width becomes large and thus the analysis area <NUM> is preferably small, but on the other hand, the statistical information of the luster material <NUM> cannot be acquired unless the analysis area <NUM> is sufficiently secured, and thus the analysis area <NUM> is preferably large from this viewpoint. By setting the two analysis areas <NUM> and <NUM> as in the third embodiment, the trade-off relationship can be simultaneously solved.

In the first to third examples, the case where the illumination pattern is the bright point <NUM> and the bright point <NUM> is moved has been described, but in a fourth example, a case where the illumination pattern is two bright lines and the bright lines are moved will be described.

As illustrated in <FIG>, vertically long bright lines <NUM> and <NUM> are displayed at both end portions of the rectangular display surface of the illumination display device <NUM> except for the intermediate portion in the vertical direction, and the bright lines <NUM> and <NUM> are moved and scanned in the horizontal direction as indicated by an arrow H3, thereby changing the illumination angle of the illumination light with respect to the measured site 100a.

On the other hand, as illustrated in <FIG>, in the image obtained by the imaging element <NUM>, both end portions of the entire rectangular light receiving area except for the intermediate portion in the vertical direction become the light receiving portions <NUM> that receive the specular reflection component on the surface of the clear layer <NUM> of the illumination light of the bright lines <NUM> and <NUM>. Then, in accordance with movement (scanning) of the bright lines <NUM> and <NUM> in the horizontal direction, the two light receiving portions <NUM> and <NUM> move in the horizontal direction (corresponding to second and third directions) H4 and H4.

In this embodiment, the analysis area <NUM> is set at a substantially center portion in the horizontal direction at the intermediate position between the two moving directions H4 and H4 of the two light receiving portions <NUM> and <NUM> in the light receiving area of the imaging element <NUM>. In the analysis area <NUM>, since the specular reflection component on the surface of the clear layer <NUM> is not received and only the specular reflection light derived from the luster material is received, the optical characteristics such as luminance and the orientation characteristics of the luster material <NUM> can be measured as in the case of the bright point <NUM>.

Further, since the analysis area is set in the region where the two light receiving portions <NUM> corresponding to the two bright lines <NUM> and <NUM> do not pass, with respect to θx'max determined by the configuration of the illumination display device <NUM>, it is possible to obtain the orientation distribution regarding θy including θy = <NUM> related to the luster material <NUM> with the luster material <NUM> having a wide range of orientation angles falling within |θx| < θx'max as a target. Note that θx'max = <NUM>° in the configuration illustrated in <FIG>, and as described above, most of the luster materials <NUM> are usually inside such an illumination angle width.

Note that, in the fourth example, two bright points may be used instead of the two bright lines <NUM> and <NUM>.

In this example, the two bright lines <NUM> and <NUM> used in the fourth embodiment are moved in the horizontal direction (x direction) and the vertical direction (y direction) of the display surface of the illumination display device <NUM>, respectively.

As illustrated in <FIG>, vertically long bright lines <NUM> and <NUM> are displayed at both end portions of the left end portion of the rectangular display surface of the illumination display device <NUM> except for the intermediate portion in the vertical direction, and the bright lines <NUM> and <NUM> are moved in the horizontal direction as indicated by arrows H5 and H5, thereby changing the illumination angle of the illumination light with respect to the measured site 100a.

Further, as illustrated in <FIG>, horizontally long bright lines <NUM> and <NUM> are displayed at both end portions of a lower end portion of the rectangular display surface of the illumination display device <NUM> except for an intermediate portion in the horizontal direction, and the illumination angle of the illumination light with respect to the measured site 100a is changed by moving these bright lines <NUM> and <NUM> in the vertical direction as indicated by arrows V4 and V4.

An image of the imaging element <NUM> corresponding to the bright lines <NUM> and <NUM> illustrated in <FIG> is illustrated in <FIG>. In this image, the both end portions in the entire rectangular light receiving area excluding the intermediate portion in the vertical direction become light receiving portions <NUM> and <NUM> that receive the specular reflection component on the surface of the clear layer <NUM> of the illumination light by the bright lines <NUM> and <NUM>. Then, according to the movement of the bright lines <NUM> and <NUM> in the horizontal direction, the two light receiving portions <NUM> and <NUM> move in the horizontal direction as indicated by arrows H6 and H6.

An image of the imaging element <NUM> corresponding to the bright lines <NUM> and <NUM> illustrated in <FIG> is illustrated in <FIG>. In this image, both end portions in the entire rectangular light receiving area excluding the intermediate portion in the horizontal direction become light receiving portions <NUM> and <NUM> that receive the specular reflection component on the surface of the clear layer <NUM> of the illumination light by the bright lines <NUM> and <NUM>. Then, according to the movement of the bright lines <NUM> and <NUM> in the vertical direction, the two light receiving portions <NUM> and <NUM> move in the vertical direction as indicated by arrows V5 and V6.

In this example, in the light receiving area of the imaging element <NUM>, the analysis area <NUM> is set at the center portion where none of the light receiving portions <NUM> for the specular reflection component on the surface of the clear layer passes when the bright lines <NUM> and <NUM> are moved in the two longitudinal and lateral directions. In the analysis area <NUM>, the specular reflection component on the surface of the clear layer <NUM> is not received and only the specular reflection light derived from the luster material is received, and thus optical characteristics such as luminance and orientation characteristics of the luster material <NUM> can be measured.

In addition, by moving the two bright lines <NUM> and <NUM> in two orthogonal directions, it is possible to obtain an orientation angle in the two orthogonal directions in each of the luster materials <NUM>. Therefore, it is possible to estimate an orientation angle (or a plane normal vector) in an arbitrary two-dimensional direction from both values.

Note that, in the fourth example, instead of the two bright lines <NUM> and <NUM>, two bright points may be moved in the vertical direction and the horizontal direction.

The present invention is not limited to the examples described above and may be modified within the scope defined by the appended claims.

For example, the sample <NUM> on which a paint including the luster material <NUM> is applied on a surface has been exemplified, but even when the luster material <NUM> is not included, when treatment such as alumite treatment is applied, minute irregularities and gradients exist in a micro region on the order of several µm to several tens µm on the surface. Due to the minute structure, a part of the surface looks sparkly when illuminated and observed from a specific direction, or another part shines when illuminated and observed from another direction, or the like, which is a driving force for expression of high design quality. Therefore, even if the luster material <NUM> is not present, it is possible to similarly measure the optical characteristics of the sample <NUM> having minute irregularities and gradients on the surface, such as a sample subjected to alumite treatment.

This application claims the priority of <CIT>.

Claim 1:
An optical characteristics measuring device, comprising:
an illumination device (<NUM>) capable of illuminating a measured site (100a) of a measurement object (<NUM>) with illumination light of which an illumination angle is changed to a plurality of illumination angles;
an imaging element (<NUM>) configured to receive reflected light from the measured site (100a) of each beam of the illumination light having the illumination angle changed and converts the reflected light into an image; and
an analysis unit (<NUM>) configured to set, as an analysis area (<NUM>), a specific area at a position in the image where a specular reflection component reflected by a surface of the measured site (100a) is not received with respect to any beam of the illumination light having the illumination angle changed in a light receiving area in the imaging element (<NUM>), and analyze an optical characteristic of the measured site (100a) on the basis of a light reception result in the analysis area (<NUM>) when the measured site (100a) is irradiated with each beam of the illumination light, wherein
the illumination device (<NUM>) is a single illumination display device configured to change the illumination angle into the plurality of illumination angles by moving a display position of a specific illumination pattern, and
a moving direction of the illumination pattern is a direction parallel and/or perpendicular to a plane formed by a normal of the measured site (100a), a normal of the illumination display device, and a normal of the imaging element (<NUM>); wherein
the imaging element (<NUM>) is a two-dimensional imaging element in which an entire light receiving area is larger than a light receiving portion (<NUM>) of the specular reflection component reflected by the surface of the measured site (100a) by one beam of illumination light; and wherein
the analysis unit (<NUM>) is configured to set the analysis area (<NUM>) at a position shifted in a direction perpendicular to a first direction, the first direction being the direction in which the position of the light receiving portion (<NUM>) of the imaging element (<NUM>) for the specular reflection component reflected by the surface of the measured site (100a) sequentially moves in response to the change in the illumination angle of the illumination light.