Patent Publication Number: US-2018052114-A1

Title: Inspection apparatus, inspection method, and program

Description:
TECHNICAL FIELD 
     The present disclosure relates to an inspection apparatus, an inspection method, and a program, and relates, in particular, to an inspection apparatus, an inspection method, and a program that allow for more accurate inspection results to be acquired. 
     BACKGROUND ART 
     An inspection apparatus is hitherto known that inspects vegetation such as state and activity of a plant raised at a certain location (refer, for example, to PTL 1). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] 
     JP 2003-9664 A 
     SUMMARY 
     Technical Problem 
     However, it was difficult to acquire accurate inspection results with such an inspection apparatus. 
     The present disclosure has been devised in light of the foregoing, and it is an object of the disclosure to allow for acquisition of more accurate inspection results. 
     Technical Solution 
     An inspection apparatus of an aspect of the present disclosure includes a calculation process section. The calculation process section calculates an inspection value for inspecting an inspection target by using sensing data having conflicting inspection-related-angle-dependent components such that the inspection-related-angle-dependent components included in sensing data acquired by sensing the inspection target are reduced. 
     An inspection method of an aspect of the present disclosure includes calculating an inspection value for inspecting an inspection target by using sensing data having conflicting inspection-related-angle-dependent components such that the inspection-related-angle-dependent components included in sensing data acquired by sensing the inspection target are reduced. 
     A program of an aspect of the present disclosure causes a computer to function as a calculation process section. The calculation process section calculates an inspection value for inspecting an inspection target by using sensing data having conflicting inspection-related-angle-dependent components such that the inspection-related-angle-dependent components included in sensing data acquired by sensing the inspection target are reduced. 
     In an aspect of the present disclosure, an inspection value is calculated for inspecting an inspection target by using sensing data having conflicting inspection-related-angle-dependent components such that the inspection-related-angle-dependent components included in sensing data acquired by sensing the inspection target are reduced. 
     Advantageous Effect of Invention 
     According to an aspect of the present disclosure, it is possible to acquire more accurate inspection results. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration example of an embodiment of a vegetation inspection system to which the present technology is applied. 
         FIG. 2  is a diagram describing definitions of a grain angle, an imaging direction angle, and a shining direction angle. 
         FIG. 3  is a diagram describing a state free from angle-dependent effects. 
         FIG. 4  is a diagram describing a first inspection condition. 
         FIG. 5  is a diagram describing a second inspection condition. 
         FIG. 6  is a diagram describing a third inspection condition. 
         FIG. 7  is a diagram describing a fourth inspection condition. 
         FIG. 8  is a diagram describing a fifth inspection condition. 
         FIG. 9  is a diagram describing a sixth inspection condition. 
         FIG. 10  is a diagram describing a seventh inspection condition. 
         FIG. 11  is a diagram describing an eighth inspection condition. 
         FIG. 12  is a diagram describing a ninth inspection condition. 
         FIG. 13  is a diagram describing a tenth inspection condition. 
         FIG. 14  is a block diagram illustrating a configuration example of a vegetation inspection apparatus. 
         FIG. 15  is a diagram describing a process performed by a calculation process section. 
         FIG. 16  is a flowchart describing an example of a process for finding a vegetation index. 
         FIG. 17  is a block diagram illustrating a configuration example of an embodiment of a computer to which the present technology is applied. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     A detailed description will be given below of an embodiment of a vegetation inspection system to which the present technology is applied with reference to drawings. 
     &lt;Embodiment of Vegetation Inspection System&gt; 
     A description will be given of a configuration example of an embodiment of a vegetation inspection system to which the present technology is applied with reference to  FIG. 1 . 
     As illustrated in  FIG. 1 , a vegetation inspection system  11  is configured to include two imaging apparatuses  12 - 1  and  12 - 2  and a vegetation inspection apparatus  13 . Then, the vegetation inspection system  11  inspects, for example, plant vegetation, targeting various plants such as lawn, rice, and sugar canes raised in a field  14  as inspection targets. Also, during inspection of plant vegetation by the vegetation inspection system  11 , sunlight is shone on the field  14  or obstructed by clouds. 
     The imaging apparatuses  12 - 1  and  12 - 2  are fastened in accordance with given arrangement conditions with respect to the field  14  and communicate with the vegetation inspection apparatus  13  via a wiredly or wirelessly constructed communication network. Then, each of the imaging apparatuses  12 - 1  and  12 - 2  takes an image of the field  14  under control of the vegetation inspection apparatus  13  and sends the image of the field  14  acquired as a result thereof to the vegetation inspection apparatus  13 . 
     For example, the imaging apparatuses  12 - 1  and  12 - 2  are fastened under the arrangement conditions in which the imaging apparatuses  12 - 1  and  12 - 2  are located at the same distance from the center of the field  14  on a straight line that passes the center of the field  14  and in which the imaging apparatuses  12 - 1  and  12 - 2  are at the same height from the field  14  and at the same elevation angle toward the center of the field  14 . That is, as illustrated in  FIG. 1 , the imaging apparatuses  12 - 1  and  12 - 2  are fastened in such a manner as to face the azimuths opposite to each other so that angles formed by optical axes of the imaging apparatuses  12 - 1  and  12 - 2  relative to the perpendicular line on the center of the flat field  14  are the same. 
     The vegetation inspection apparatus  13  controls timings when the imaging apparatuses  12 - 1  and  12 - 2  take images of the field  14 . Then, the vegetation inspection apparatus  13  finds a vegetation index for inspecting vegetation of a plant raised in the field  14  on the basis of images of the field  14  taken by the imaging apparatuses  12 - 1  and  12 - 2 . It should be noted that the detailed configuration of the vegetation inspection apparatus  13  will be described later with reference to  FIG. 14 . 
     The vegetation inspection system  11  configured as described above can find a vegetation index free from (with reduced) angle-dependent effect for each of directions in which the plant raised in the field  14  grows, in which the imaging apparatuses  12 - 1  and  12 - 2  take images of the field  14 , in which light is shone on the field  14  from the sun. 
     For example, in a case where a lawn is raised in the field  14 , the direction in which the lawn grows (hereinafter referred to as the grain) varies significantly depending on mowing thereof. Therefore, it is difficult to constantly inspect vegetation under the same conditions. For this reason, a description will be given below assuming that a lawn is inspected by the vegetation inspection system  11  in the field  14  where the lawn as can be found in a soccer stadium is raised. Of course, not only the above-described rice and sugar canes but also various other plants can be subject to inspection by the vegetation inspection system  11 . 
     For example, hatching directions of the field  14  in  FIG. 1  indicate the grains of the lawn raised in the field  14 , and the vegetation inspection system  11  is capable of inspecting vegetation in a manner free from any effect of the grain angle of the lawn that is raised such that the grain differs from one given area to another. It should be noted that each of the imaging apparatuses  12 - 1  and  12 - 2  will be simply referred to as the imaging apparatuses  12  as appropriate in a case where it is not necessary to distinguish between the imaging apparatuses  12 - 1  and  12 - 2 . 
     &lt;Definitions of Azimuth Angle and Elevation Angle&gt; 
     A description will be given of the grain angle in the field  14 , the angle of the imaging direction by the imaging apparatuses  12 , and the angle of the shining direction of light shone on the field  14  with reference to  FIG. 2 . 
     As illustrated in A of  FIG. 2 , for example, a grain angle P in the field  14  is defined on the basis of an azimuth angle θ of the grain with respect to a given reference direction and an elevation angle φ of the grain with respect to a vertically upward direction. That is, in a case where the azimuth angle θ of the grain is “a” and the elevation angle φ of the grain is “b,” the grain angle is defined as P(a,b). It should be noted that in a case where the grain points vertically upward, the grain angle is P(0,0). 
     Also, as illustrated in B of  FIG. 2 , an angle C of an imaging direction by the imaging apparatuses  12  is defined on the basis of the azimuth angle θ of the imaging direction with respect to a given reference direction and the elevation angle φ of the imaging direction with respect to a vertically downward direction. That is, in a case where the azimuth angle θ of the imaging direction is “c” and the elevation angle φ of the imaging direction is “d,” the imaging direction angle is defined as C(c,d). It should be noted that in a case where the imaging direction points vertically downward, the imaging direction angle is C(0,0). 
     Similarly, as illustrated in C of  FIG. 2 , an angle L of the direction of light shone on the field  14  is defined on the basis of the azimuth angle θ of the shining direction with respect to a given reference direction and the elevation angle φ of the shining direction with respect to the vertically downward direction. That is, in a case where the azimuth angle θ of the shining direction is “e” and the elevation angle φ of the shining direction is “f,” the shining direction angle is defined as L(e,f). 
     It should be noted that in a case where the shining direction points vertically downward, the shining direction angle is L(0,0). 
     Then, when the grain angle P(0,0), the imaging direction angle C(0,0), and the shining direction angle L(0,0) are all satisfied, inspection can be conducted in a manner free from effects dependent upon these angles as illustrated in  FIG. 3 . 
     However, it is difficult to conduct inspection such that the grain angle P(0,0), the imaging direction angle C(0,0), and the shining direction angle L(0,0) are all satisfied. For this reason, the vegetation inspection system  11  is capable of eliminating effects dependent upon these angles using inspection conditions as illustrated with reference to  FIGS. 4 to 13 . That is, the grain angle, the imaging direction angle, and the shining direction angle are angles related to inspection of the field  14  by the vegetation inspection apparatus  13 , and effects dependent upon these angles manifest themselves in images taken by the imaging apparatuses  12 . Therefore, the vegetation inspection system  11  conducts vegetation inspection by using images taken under inspection conditions where the components dependent upon these inspection-related angles (e.g., azimuth angle θ, elevation angle φ) conflict with each other. 
     &lt;Inspection Conditions that Eliminate Angle-Dependent Effects&gt; 
     A description will be given of a first inspection condition for eliminating angle-dependent effects with reference to  FIG. 4 . 
     As illustrated in  FIG. 4 , when the grain angle is P(0,0) and the imaging direction angle is C(0,0), it is possible to eliminate angle-dependent effects by performing imaging twice, with the shining direction angles L(e,f) and L(−e,f). That is, in the first inspection condition, the grain points vertically upward, and imaging is performed vertically downward from directly above twice when the light shining directions are at symmetrical angles relative to the vertical direction (at opposite azimuth angles). 
     By taking the arithmetic mean of the two images taken under the inspection condition described above, the difference in shining direction angle is cancelled (the shining direction angle becomes equivalent to L(0,0)), making it possible to eliminate the effect dependent upon the shining direction angle. 
     A description will be given of a second inspection condition for eliminating angle-dependent effects with reference to  FIG. 5 . 
     As illustrated in  FIG. 5 , when the grain angle is P(0,0) and the shining direction angle is L(0,0), it is possible to eliminate angle-dependent effects by performing imaging from two directions where the imaging direction angles are C(c,d) and C(−c,d). That is, in the second inspection condition, the grain points vertically upward, and imaging is performed from two directions where the imaging directions are at symmetrical angles relative to the vertical direction when light is shone vertically downward from directly above. 
     By taking the arithmetic mean of the two images taken under the second inspection condition described above, the difference in imaging direction angle is cancelled (the imaging direction angle becomes equivalent to C(0,0)), making it possible to eliminate effects dependent upon the imaging direction angle. 
     A description will be given of a third inspection condition for eliminating angle-dependent effects with reference to  FIG. 6 . 
     As illustrated in  FIG. 6 , it is possible to eliminate angle-dependent effects by performing first imaging with the shining direction angle L(e,f) and the imaging direction angle C(c,d) and performing second imaging with the shining direction angle L(−e,f) and the imaging direction angle C(−c,d) when the grain angle is P(0,0). That is, in the third inspection condition, the grain points vertically upward, and imaging is performed from two directions where the imaging directions are at symmetrical angles relative to the vertical direction and twice, and each time when the light shining directions are at symmetrical angles relative to the vertical direction. 
     By taking the arithmetic mean of the two images taken under the third inspection condition described above, the differences in imaging direction angle and shining direction angle are cancelled (the imaging direction angle becomes equivalent to C(0,0) and the shining direction angle becomes equivalent to L(0,0)), making it possible to eliminate effects dependent upon the imaging direction angle and the shining direction angle. 
     A description will be given of a fourth inspection condition for eliminating angle-dependent effects with reference to  FIG. 7 . 
     As illustrated in  FIG. 7 , it is possible to eliminate angle-dependent effects by taking images of two areas where the grain angles are P(a,b) and P(−a,b) when the shining direction angle is L(0,0) and the imaging direction angle is C(0,0). That is, in the fourth inspection condition, imaging is performed vertically downward when light is shone vertically downward to take images of two areas where the grain is at symmetrical angles relative to the vertically upward direction. 
     By taking the arithmetic mean of the two images taken under the fourth inspection condition described above, the difference in grain angle is cancelled (the grain angle becomes equivalent to P(0,0)), making it possible to eliminate the effect dependent upon the grain angle. As will be described later, for example, in a case where two areas whose grain angle components conflict with each other are included in a single image, it is possible to reduce the effect dependent upon the grain angle by taking the arithmetic mean of sensing values of two areas as sensing data. 
     A description will be given of a fifth inspection condition for eliminating angle-dependent effects with reference to  FIG. 8 . 
     As illustrated in  FIG. 8 , when the shining direction angle is L(0,0), it is possible to eliminate angle-dependent effects by taking an image of an area having the grain angle P(a,b) at the imaging direction angle C(c,d) and taking an image of an area having the grain angle P(−a,b) at the imaging direction angle C(−c,d). That is, in the fifth inspection condition, imaging is performed from two directions at symmetrical angles relative to the vertically downward direction to take images of two respective areas where the grain is at symmetrical angles relative to the vertically upward direction when light is shone vertically downward. 
     By taking the arithmetic mean of the two images taken under the fifth inspection condition described above, the differences in grain angle and imaging direction angle are cancelled (the grain angle becomes equivalent to P(0,0) and the imaging direction angle becomes equivalent to C(0,0)), making it possible to eliminate the effects dependent upon the grain angle and imaging direction angle. 
     A description will be given of a sixth inspection condition for eliminating angle-dependent effects with reference to  FIG. 9 . 
     As illustrated in  FIG. 9 , it is possible to eliminate angle-dependent effects by performing first imaging to take an image of an area having the grain angle P(a,b) from the imaging direction angle C(c,d) when the shining direction angle reaches L(e,f) and performing second imaging to take an image of an area having the grain angle P(−a,b) from the imaging direction angle C(−c,d) when the shining direction angle reaches L(−e,f). That is, in the sixth inspection condition, imaging is performed from two directions at symmetrical angles relative to the vertically downward direction to take images of two respective areas where the grain is at symmetrical angles relative to the vertically upward direction, and imaging is performed at two timings when the light shining directions are at symmetrical angles relative to the vertical direction. 
     By taking the arithmetic mean of the two images taken under the sixth inspection condition described above, the differences in grain angle, imaging direction angle, and shining direction are cancelled (the grain angle becomes equivalent to P(0,0), and the imaging direction angle becomes equivalent to C(0,0), and the shining direction angle becomes equivalent to L(0,0)), making it possible to eliminate the effects dependent upon the grain angle, imaging direction angle, and shining direction angle. 
     Incidentally, in  FIGS. 4 to 9 , a description has been given of situations in which effects dependent upon the angle of shining direction of light shone on the lawn are sustained, that is, situations in which the sun is out during daytime. It should be noted, however, that there are only limited locations where the sun comes overhead, and it is presumably difficult to completely eliminate effects dependent upon the shining direction angle by using an east/west combination alone. For this reason, in order to eliminate effects dependent upon the shining direction angle, it is possible to make use of the condition in which there is no direct shining of sunlight, that is, the condition in which light is diffused in cloudy or rainy weather, before the sunrise, after the sunset, and so on. 
     That is, in a case where the weather is cloudy with no sunlight directly shone on the field  14 , there is no need to consider the effect dependent upon the shining direction angle (it is acceptable to consider that the shining direction is equivalent to angle L(0,0)). In seventh to tenth inspection conditions for eliminating angle-dependent effects which will be described below, imaging is performed in cloudy weather. 
     A description will be given of a seventh inspection condition for eliminating angle-dependent effects with reference to  FIG. 10 . 
     As illustrated in  FIG. 10 , it is possible to eliminate angle-dependent effects by performing imaging once at the imaging direction angle C(0,0) when the grain angle is P(0,0). That is, in the seventh inspection condition, the grain points vertically upward, and imaging is performed vertically downward from directly above. That is, in this case, it is possible to eliminate angle-dependent effects using images acquired by a single occasion of imaging. 
     A description will be given of an eighth inspection condition for eliminating angle-dependent effects with reference to  FIG. 11 . 
     As illustrated in  FIG. 11 , when the grain angle is P(0,0), it is possible to eliminate angle-dependent effects by performing imaging from two directions where the imaging direction angles are C(c,d) and C(−c,d). That is, in the eighth inspection condition, the grain points vertically upward, and imaging is performed from two directions where the imaging directions are at symmetrical angles relative to the vertical direction. 
     By taking the arithmetic mean of the two images taken under the eighth inspection condition described above, the difference in imaging direction angle is cancelled (the imaging direction angle becomes equivalent to C(0,0)), making it possible to eliminate the effect dependent upon the imaging direction angle. 
     A description will be given of a ninth inspection condition for eliminating angle-dependent effects with reference to  FIG. 12 . 
     As illustrated in  FIG. 12 , when the imaging direction angle is C(0,0), it is possible to eliminate the angle-dependent effect by taking images of two areas where the grain angles are P(a,b) and P(−a,b). That is, in the ninth inspection condition, imaging is performed vertically downward to take images of two areas where the grain is at symmetrical angles relative to the vertically upward direction. 
     By taking the arithmetic mean of the two images taken under the ninth inspection condition described above, the difference in grain angle is cancelled (the grain angle becomes equivalent to P(0,0)), making it possible to eliminate the effect dependent upon the grain angle. 
     A description will be given of a tenth inspection condition for eliminating angle-dependent effects with reference to  FIG. 13 . 
     As illustrated in  FIG. 13 , it is possible to eliminate angle-dependent effects by taking an image of an area having the grain angle P(a,b) at the imaging direction angle C(c,d) and taking an image of an area having the grain angle P(−a,b) at the imaging direction angle C(−c,d). That is, in the tenth inspection condition, imaging is performed from two directions at symmetrical angles relative to the vertically downward direction to take images of two respective areas where the grain is at symmetrical angles relative to the vertically upward direction. 
     By taking the arithmetic mean of the two images taken under the tenth inspection condition described above, the differences in grain angle and imaging direction angle are cancelled (the grain angle becomes equivalent to P(0,0) and the imaging direction angle becomes equivalent to C(0,0)), making it possible to eliminate the effects dependent upon the grain angle and imaging direction angle. 
     &lt;Configuration Example of Vegetation Inspection Apparatus&gt; 
       FIG. 14  is a block diagram illustrating a configuration example of the vegetation inspection apparatus  13 . 
     As illustrated in  FIG. 14 , the vegetation inspection apparatus  13  is configured to include a communication section  21 , a data server  22 , a weather information acquisition section  23 , an imaging control section  24 , and a calculation process section  25 , and the imaging apparatuses  12 - 1  and  12 - 2  are connected to the vegetation inspection apparatus  13 . Here, the imaging apparatuses  12 - 1  and  12 - 2  are configured to include, for example, a sensor that has not only detection devices for each detecting red, green, and blue light in the visible range but also detection devices for detecting near-infrared (NIR) outside the visible range. The detection devices are arranged two-dimensionally. The imaging apparatuses  12 - 1  and  12 - 2  are used as sensing apparatuses for sensing light from the field  14 . That is, the imaging apparatuses  12 - 1  and  12 - 2  include an imaging sensor that has pixels (detection devices) arranged two-dimensionally, for detecting light in different wavelength ranges for the respective wavelength ranges, and images for the respective wavelength ranges taken with the imaging sensor (image data including sensing values) are an example of sensing data acquired by sensing. 
     The communication section  21  communicates with the imaging apparatuses  12 - 1  and  12 - 2 . For example, the communication section  21  receives image data making up images taken with the imaging apparatuses  12 - 1  and  12 - 2  (e.g., Raw data made up of red (R), green (G), blue (B), and infrared (IR) pixel values) and supplies the image data to the data server  22 . Also, when supplied with an imaging command instructing the imaging apparatuses  12 - 1  and  12 - 2  to perform imaging from the imaging control section  24 , the communication section  21  sends the imaging command to the imaging apparatuses  12 - 1  and  12 - 2 . 
     The data server  22  accumulates image data supplied from the communication section  21  and supplies image data to the calculation process section  25  in response to a request from the calculation process section  25 . The data server  22  also acquires weather information at the time of image taking by the imaging apparatuses  12 - 1  and  12 - 2  via the weather information acquisition section  23  and stores the weather information in association with image data corresponding to the image. 
     The weather information acquisition section  23  acquires, for example, weather information observed by an observational instrument (not illustrated) installed in the field  14  or weather information in the neighborhood of the field  14  delivered via an external network such as the Internet and supplies such weather information to the imaging control section  24  as required. The weather information acquisition section  23  also supplies, to the data server  22 , weather information at the time of taking of image data accumulated in the data server  22 . 
     The imaging control section  24  sends an imaging command instructing the imaging apparatuses  12 - 1  and  12 - 2  to perform imaging to the imaging apparatuses  12 - 1  and  12 - 2  via the communication section  21  in accordance with time information measured by a built-in timer (e.g., data including date, hours, minutes, and seconds) or weather information supplied from the weather information acquisition section  23 . As a result, the imaging control section  24  controls timings when the imaging apparatuses  12 - 1  and  12 - 2  image the field  14 . 
     For example, the imaging control section  24  sends an imaging command when the angle of shining direction of light shone on the field  14  reaches L(0,0) as described above with reference to  FIGS. 5, 7, and 8  in accordance with time information measured by the built-in timer. The imaging control section  24  also sends an imaging command when the angle of shining direction of light shone on the field  14  reaches L(e,f) and L(−e,f) as described above with reference to  FIGS. 4, 6, and 9  in accordance with time information measured by the built-in timer. The imaging control section  24  also sends an imaging command when the weather at the field  14  turns cloudy as described above with reference to  FIGS. 10 to 13  in accordance with the weather information supplied from the weather information acquisition section  23 . 
     The calculation process section  25  reads image data accumulated in the data server  22  and calculates a vegetation index of the field  14  free from angle-dependent effects using a set of images taken with the imaging apparatuses  12 - 1  and  12 - 2 . That is, the calculation process section  25  is configured to include, as illustrated, a vegetation index calculation section  31 , a lens distortion correction section  32 , an addition process section  33 , a cancellation process section  34 , and an integration process section  35 . 
     When image data of a set of images taken with the imaging apparatuses  12 - 1  and  12 - 2  is accumulated in the data server  22 , the vegetation index calculation section  31  reads these pieces of image data from the data server  22  and calculates a vegetation index for use as an inspection value for inspecting vegetation. 
     For example, in a case where the vegetation inspection system  11  uses a normalized difference vegetation index (NDVI), an index indicating vegetation distribution condition and activity, the normalized difference vegetation index NDVI can be calculated by computing the following Formula (1). As illustrated in Formula (1), the normalized difference vegetation index NDVI can be found by using a pixel value R representing the red component in the visible range and a pixel value IR representing the component in the near-infrared range. 
       [Formula 1] 
       NDVI=IR−R/IR+R  (1)
 
     Therefore, the vegetation index calculation section  31  finds the normalized difference vegetation index NDVI for each of the pixels making up each of the images by using the pixel value R and the pixel value IR of the image data acquired by imaging of the field  14  by the respective imaging apparatuses  12 - 1  and  12 - 2 . Then, the vegetation index calculation section  31  generates two NDVI images on the basis of the pixel values of the two images taken with the imaging apparatuses  12 - 1  and  12 - 2 . 
     The lens distortion correction section  32  corrects lens distortion of the two NDVI images generated by the vegetation index calculation section  31 . 
     That is, as illustrated in  FIG. 1 , lens distortion is present in the images taken from the imaging directions at given elevation angles relative to the field  14  when a wide-angle lens (e.g., fish-eye lens) was attached to the imaging apparatuses  12 - 1  and  12 - 2  to take images of the entire field  14 . Therefore, similar lens distortion is present in the NDVI images generated on the basis of such images. For example, the straight lines in the field  14  are curved in the peripheral areas of the NDVI images. Therefore, the lens distortion correction section  32  corrects the lens distortion present in the NDVI images such that the straight lines in the field  14  are also straight in the peripheral areas of the NDVI images. 
     The addition process section  33  performs a process of taking the arithmetic mean of the two NDVI images whose lens distortion has been corrected by the lens distortion correction section  32 , generating a single NDVI image with cancelled difference in imaging direction angle. 
     In the cancellation process section  34 , information is registered in advance about the azimuth angle of the lawn for each of the areas distinguished by grain of the lawn raised in the field  14  (e.g., which area has what kind of grain). Then, the cancellation process section  34  cancels the difference in grain angle in the NDVI image generated by the addition process section  33  by adding the pixel values of some of the areas in the two-dimensional sensing data whose azimuth angles of the grain are opposite to each other. 
     The integration process section  35  performs a process of taking the mean of the area data that has been added up by the cancellation process section  34 , dividing the data into areas distinguished by grain and integrating the data for the normalized difference vegetation index NDVI in which the difference in grain angle is cancelled by the cancellation process section  34 . 
     The vegetation inspection apparatus  13  configured as described above makes it possible to acquire vegetation information (NDVI image) free from the effects dependent upon the grain angle, imaging direction angle, and shining direction angle. 
     A description will be given of a process performed by the calculation process section  25 , for example, under the tenth inspection condition illustrated in  FIG. 13  with reference to  FIG. 15 . 
     In the field  14 , for example, a lawn is raised such that four areas with the different grain angles P(a,b) are arranged alternately. That is, an area with the grain angle P(a1,b1), an area with the grain angle P(a2,b2), an area with the grain angle P(a3,b3), and an area with the grain angle P(a4,b4) are arranged, two down and two across, and these four areas are laid over the entire field  14 . 
     Then, when the weather is cloudy, the field  14  is imaged from the imaging direction at the angle C(c,d) by the imaging apparatus  12 - 1 , and the field  14  is imaged from the imaging direction at the angle C(−c,d) by the imaging apparatus  12 - 2 . 
     At this time, lens distortion is present in an NDVI image P 1  generated by the vegetation index calculation section  31  from the image taken with the imaging apparatus  12 - 1  in accordance with the imaging direction angle C(c,d) by the imaging apparatus  12 - 1 . Similarly, lens distortion is present in an NDVI image P 2  generated by the vegetation index calculation section  31  from the image taken with the imaging apparatus  12 - 2  in accordance with the imaging direction angle C(−c,d) by the imaging apparatus  12 - 2 . 
     Therefore, the lens distortion correction section  32  generates an NDVI image P 3  with corrected lens distortion of the NDVI image P 1  and generates an NDVI image P 4  with corrected lens distortion of the NDVI image P 2 . Here, each of rectangles illustrated in a grid pattern in the NDVI images P 3  and P 4  represents each of the areas distinguished in accordance with the grain angle P(a,b), and each of arrows illustrated in each of the rectangles indicates the grain angle P(a,b). 
     At this time, the normalized difference vegetation index NDVI of each of the pixels making up the NDVI image P 3  includes a component dependent upon the grain angle P(a,b) and a component dependent upon the imaging direction angle C(c,d). Similarly, the normalized difference vegetation index NDVI of each of the pixels making up the NDVI image P 4  includes a component dependent upon the grain angle P(a,b) and a component dependent upon the imaging direction angle C(−c,d). 
     Then, the addition process section  33  performs a process of taking the arithmetic mean of the NDVI images P 3  and P 4 , generating an NDVI image P 5  in which the component dependent upon the imaging direction angle C(c,d) and the component dependent upon the imaging direction angle C(−c,d) have cancelled each other out. That is, the NDVI image P 5  becomes equivalent to the imaging direction angle C(0,0). It should be noted that the shining direction angle is L(0,0) because imaging is performed in cloudy weather. 
     Next, the cancellation process section  34  performs a process of cancelling the component dependent upon the grain angle P(a,b) included in the NDVI image P 5 . 
     For example, the azimuth angles θ of the grain angle P(a1,b1) and the grain angle P(a3,b3) are opposite to each other, and the azimuth angles θ of the grain angle P(a2,b2) and the grain angle P(a4,b4) are opposite to each other. Therefore, the cancellation process section  34  can cancel the component dependent upon the grain angle P(a,b) by adding the normalized difference vegetation index NDVI of the area with the grain angle P(a1,b1), the normalized difference vegetation index NDVI of the area with the grain angle P(a2,b2), the normalized difference vegetation index NDVI of the area with the grain angle P(a3,b3), and the normalized difference vegetation index NDVI of the area with the grain angle P(a4,b4). 
     At this time, the cancellation process section  34  performs a process of adding the normalized difference vegetation indices NDVI such that the two of the four areas subject to addition overlap each other as illustrated on the right of the NDVI image P 5 . 
     As a result, all the components dependent upon angles are cancelled from the normalized difference vegetation index NDVI, and the normalized difference vegetation index NDVI equivalent to the grain angle P(0,0), the imaging direction angle C(0,0), and the shining direction angle L(0,0) is acquired. 
     Thereafter, the integration process section  35  performs a process of taking the mean of the data of the four areas, dividing the data into area-by-area information for each grain angle P(a,b) and integrating the data, outputting an NDVI image P 6  made up of the normalized difference vegetation index NDVI of the entire field  14  free from angle dependence. That is, as illustrated on the right side of the NDVI image P 6 , assuming a certain area to be a center, the integration process section  35  takes the mean by adding up the mean of the four areas having that area at bottom right, the mean of the four areas having that area at bottom left, the mean of the four areas having that area at top right, and the mean of the four areas having that area at top left, and uses the mean as the normalized difference vegetation index NDVI of that area. The integration process section  35  performs such averaging for all areas. 
     This allows the integration process section  35  to output the NDVI image P 6  made up of the normalized difference vegetation index NDVI of the entire field  14  free from angle dependence. It should be noted that the calculation process section  25  may find a vegetation index other than the normalized difference vegetation index NDVI (e.g., ratio vegetation index (RVI) or green NDVI (GNDVI)) by using a pixel value R representing a red component in the visible range, a pixel value G representing a green component in the visible range, a pixel value B representing a blue component in the visible range, and a pixel value IR representing a component in the near-infrared range. 
     &lt;Processing for Finding Vegetation Index&gt; 
       FIG. 16  is a flowchart describing an example of a process for the vegetation inspection system  11  to find a vegetation index. 
     In step S 11 , the weather information acquisition section  23  acquires weather information in the field  14  and supplies the information to the imaging control section  24 . 
     In step S 12 , the imaging control section  24  decides whether or not it is time for the imaging apparatuses  12 - 1  and  12 - 2  to image the field  14 . For example, when the weather is cloudy to such an extent that the field  14  remains unaffected by the angle L(θ,φ) of the light shining direction from the sun on the basis of weather information supplied from the weather information acquisition section  23  in step S 11 , the imaging control section  24  decides that it is time to perform imaging. Alternatively, the imaging control section  24  may decide whether or not it is time to perform imaging on the basis of time information as described above. 
     In a case where the imaging control section  24  decides in step S 12  that it is not time for the imaging apparatuses  12 - 1  and  12 - 2  to take images of the field  14 , the process returns to step S 11  to repeat the same processes from here onward. On the other hand, in a case where the imaging control section  24  decides in step S 12  that it is time for the imaging apparatuses  12 - 1  and  12 - 2  to take images of the field  14 , the process proceeds to step S 13 . 
     In step S 13 , the imaging control section  24  sends, to the imaging apparatuses  12 - 1  and  12 - 2 , an imaging command instructing to perform imaging via the communication section  21 , and the imaging apparatuses  12 - 1  and  12 - 2  take images of the field  14  in accordance with the imaging command. Then, each of the imaging apparatuses  12 - 1  and  12 - 2  sends the taken image of the field  14 , and the communication section  21  acquires the image data of these images and accumulates the data in the data server  22 . 
     In step S 14 , the vegetation index calculation section  31  reads two images worth of image data to be processed from the data server  22  and computes the above Formula (1), finding the normalized difference vegetation index NDVI for each pixel making up each image and generating two NDVI images. 
     In step S 15 , the lens distortion correction section  32  performs a process of correcting lens distortion on each of the two NDVI images generated by the vegetation index calculation section  31  in step S 14 , generating two NDVI images with corrected lens distortion. 
     In step S 16 , the addition process section  33  performs a process of taking the arithmetic mean of the two NDVI images whose lens distortion has been corrected by the lens distortion correction section  32  in step S 15 , generating a single NDVI image with cancelled component dependent upon the imaging direction angle. 
     In step S 17 , the cancellation process section  34  adds the areas whose grain angles are opposite to each other in the NDVI image generated by the addition process section  33  in step S 16 , cancelling the component dependent upon the grain angle. 
     In step S 18 , the integration process section  35  divides the NDVI image whose component dependent upon the grain angle has been cancelled by the cancellation process section  34  in step S 17  into grain areas and integrates the image. 
     Then, after the process in step S 18 , the process returns to step S 11  to repeat the similar processes from here onward. 
     As described above, the vegetation inspection system  11  makes it possible to acquire an NDVI image made up of the normalized difference vegetation index NDVI of the entire field  14  by cancelling the component dependent upon the grain angle and cancelling the component dependent upon the imaging direction angle. Therefore, it is possible to inspect vegetation of the lawn raised in the field  14  by eliminating the effects dependent upon the grain angle, imaging direction angle, and shining direction angle using the vegetation inspection system  11 . 
     It should be noted that, in order to cancel the effects dependent upon the grain angle, imaging direction angle, and shining direction angle in the present embodiment, an arithmetic mean process is performed by using images whose corresponding positive and negative components of the respective angles completely conflict with each other for ease of comprehension. For the imaging direction, for example, an arithmetic mean process is performed by using images from two directions at the imaging direction angles C(c,d) and C(−c,d). In contrast, actually, even if images with completely conflicting positive and negative components of the angles are not used, and, for example, as long as the components conflict with each other within a given reference value such as 5% or 10%, it is possible to reduce the angle-dependent effects by using such images. Further, the grain angle, imaging direction angle, and shining direction angle are merely examples of angles related to inspection of the field  14 , and other angles may also be used. 
     It should be noted that although a configuration for taking two images with the two imaging apparatuses  12 - 1  and  12 - 2  has been described in the present embodiment, for example, the normalized difference vegetation index NDVI may be calculated from two images taken successively by moving the single imaging apparatus  12 . For example, imaging may be performed at an arbitrary position by mounting the imaging apparatus  12  to an unmanned aerial vehicle (UAV). Further, two or more imaging apparatuses  12  may be used, and, for example, the normalized difference vegetation index NDVI may be calculated from four images taken from east-west and north-south directions using the four imaging apparatuses  12 . 
     Further, it is not necessary to provide the lens distortion correction section  32  if images free from lens distortion can be taken. It should be noted that in addition to a configuration in which the imaging apparatuses  12  and the vegetation inspection apparatus  13  are connected via a communication network, images may be supplied via a recording medium, for example, with the imaging apparatuses  12  and the vegetation inspection apparatus  13  put offline. In this case, there is no need to provide the data server  22 . Also, the imaging apparatuses  12  and the vegetation inspection apparatus  13  may be configured as an integral apparatus. 
     Further, for example, the imaging apparatuses  12  can find a vegetation index and send the index to the vegetation inspection apparatus  13 , and the vegetation inspection apparatus  13  can perform a process of eliminating angle-dependent effects. Also, the process of eliminating angle-dependent effects, for example, is not limited to the vertical direction as illustrated by the grain angle P(0,0), the imaging direction angle C(0,0), and the shining direction angle L(0,0) in  FIG. 3 , and it is only necessary for these angles to be at fixed angles other than the vertical direction. That is, when vegetation is compared, it is only necessary to eliminate angle-dependent effects such that the same conditions are present at all times. 
     Further, the system in the present specification refers to the apparatus as a whole made up of a plurality of apparatuses. 
     It should be noted that the respective processes described with reference to the above flowchart need not necessarily be performed chronologically in accordance with the sequence described as a flowchart and include those that are performed in parallel or individually (e.g., parallel processes or object-based processes). Further, the program may be processed by a single central processing unit (CPU) or by a plurality of CPUs in a distributed manner. 
     Further, the above series of processes may be performed by hardware or software. In a case where the series of processes are performed by software, the program making up the software is installed from a program recording medium recording the program to a computer incorporated in dedicated hardware or, for example, to a general-purpose personal computer or other computer capable of performing various functions by installing various programs. 
       FIG. 17  is a block diagram illustrating a hardware configuration example of a computer for performing the above series of processes using a program. 
     In the computer, a CPU  101 , a read only memory (ROM)  102 , and a random access memory (RAM)  103  are connected to each other by a bus  104 . 
     An input/output (I/O) interface  105  is further connected to the bus  104 . An input section  106 , an output section  107 , a storage section  108 , a communication section  109 , and a drive  110  are connected to the I/O interface  105 . The input section  106  includes a keyboard, a mouse, a microphone, and so on. The output section  107  includes a display, a speaker, and so on. The storage section  108  includes a hard disk, a non-volatile memory, and so on. The communication section  109  includes a network interface and so on. The drive  110  records information to or reads information from a removable recording medium  111  such as magnetic disk, optical disk, magneto-optical disk, or semiconductor memory. 
     In the computer configured as described above, the CPU  101  performs the above series of processes, for example, by loading the program stored in the storage section  108  into the RAM  103  via the I/O interface  105  and bus  104  for execution. 
     The program executed by the computer (CPU  101 ) is provided in a manner stored in, for example, a magnetic disk (including flexible disk), an optical disk (e.g., compact disk-read only memory (CD-ROM), digital versatile disk (DVD)), magneto-optical disk, or a removable medium  111  which is a packaged medium including semiconductor memory. Alternatively, the program is provided via a wired or wireless transmission medium such as local area network, the Internet, and digital satellite broadcasting. 
     Then, the program can be installed to the storage section  108  via the I/O interface  105  as the removable medium  111  is inserted into the drive  110 . Alternatively, the program can be received by the communication section  109  via a wired or wireless transmission medium and installed to the storage section  108 . In addition to the above, the program can be installed, in advance, to the ROM  102  or storage section  108 . 
     It should be noted that the present technology can also have the following configurations: 
     (1) An inspection apparatus including: 
     a calculation process section configured to calculate an inspection value for inspecting an inspection target by using sensing data having conflicting inspection-related-angle-dependent components such that the inspection-related-angle-dependent components included in sensing data acquired by sensing the inspection target are reduced. 
     (2) The inspection apparatus of feature (1), in which 
     the calculation process section reduces the angle-dependent components included in the sensing data in accordance with a growing direction of a plant, the inspection target, by performing a calculation process using at least two areas where azimuth angles of the growing direction of the plant, the inspection target, are opposite to each other. 
     (3) The inspection apparatus of feature (1) or (2), in which 
     the sensing data is image data including sensing values of respective wavelength ranges acquired on the basis of a sensor that has detection devices, arranged two-dimensionally, for detecting light in different wavelength ranges for the respective wavelength ranges. 
     (4) The inspection apparatus of feature (3), in which 
     the sensing data includes sensing values in respective red, green, blue, and near-infrared wavelength ranges. 
     (5) The inspection apparatus of any one of features (1) to (4), in which 
     the inspection target is a plant, and the inspection value is a normalized difference vegetation index. 
     (6) The inspection apparatus of any one of features (1) to (5), in which 
     the calculation process section reduces the angle-dependent component included in the sensing data in accordance with a sensing direction in which the inspection target is sensed by performing a calculation process using two pieces of the sensing data in which the azimuth angles of the sensing directions at the time of sensing the sensing data are sensed in directions opposite to each other. 
     (7) The inspection apparatus of any one of features (1) to (6), in which 
     the calculation process section reduces the angle-dependent component included in the sensing data in accordance with a shining direction of light shone on the inspection target by performing a calculation process using two pieces of the sensing data in which the azimuth angles of shining direction of light shone on the inspection target at the time of sensing the sensing data are sensed in directions opposite to each other. 
     (8) The inspection apparatus of any one of features (1) to (7), further including: 
     a sensing control section configured to control a sensing apparatus for sensing the inspection target. 
     (9) The inspection apparatus of feature (8), further including: 
     a weather information acquisition section configured to acquire weather information indicating weather of the field where a plant, the inspection target, is raised, in which 
     the sensing control section causes the sensing apparatus to sense the plant when the weather is cloudy in the field. 
     (10) The inspection apparatus of feature (8) or (9), in which 
     the sensing control section causes the sensing apparatus to sense the inspection target at a timing that is in accordance with the sensing direction of sensing the inspection target and the shining direction of light shone on the inspection target. 
     (11) The inspection apparatus of feature (1), in which 
     the sensing data is image data including sensing values of respective wavelength ranges acquired on the basis of a sensor that has detection devices, arranged two-dimensionally, for detecting light in different wavelength ranges for the respective wavelength ranges. 
     (12) The inspection apparatus of feature (11), in which 
     the sensing data includes sensing values in respective red, green, blue, and near-infrared wavelength ranges. 
     (13) The inspection apparatus of feature (12), in which 
     the inspection target is a plant, and the inspection value is a normalized difference vegetation index. 
     (14) An inspection method including: 
     calculating an inspection value for inspecting an inspection target by using sensing data having conflicting inspection-related-angle-dependent components such that the inspection-related-angle-dependent components included in sensing data acquired by sensing the inspection target are reduced. 
     (15) A program causing a computer to function as: 
     a calculation process section configured to calculate an inspection value for inspecting an inspection target by using sensing data having conflicting inspection-related-angle-dependent components such that the inspection-related-angle-dependent components included in sensing data acquired by sensing the inspection target are reduced. 
     It should be noted that the present embodiment is not limited to that described above and can be modified in various ways without departing from the gist of the present technology. 
     REFERENCE SIGNS LIST 
     
         
         
           
               11  . . . Vegetation inspection system 
               12 - 1 ,  12 - 2  . . . Imaging apparatuses 
               13  . . . Vegetation inspection apparatus 
               14  . . . Field 
               21  . . . Communication section 
               22  . . . Data server 
               23  . . . Weather information acquisition section 
               24  . . . Imaging control section 
               25  . . . Calculation process section 
               31  . . . Vegetation index calculation section 
               32  . . . Lens distortion correction section 
               33  . . . Addition process section 
               34  . . . Cancellation process section 
               35  . . . Integration process section