## 4 Experimental Results and Discussion  
In this paper, an experiment was conducted to evaluate the performance of the proposed method. The lens array used in the experiment is a 17 \(\times\) 20 array of square lenses with a focal length of 73 mm and a size of 7.47 mm \(\times\) 7.47 mm. As shown in Figure 6, three test images such as a diagonal pattern, car and bear toys, and a ruler were used for the experiment. A DSLR camera with pixels of 4000 \(\times\) 3000 was employed to capture a raw image, which is also shown in Figure 6. Typical images seen through the lens array are prepared as the inputs of proposed and existing methods. To evaluate objectively, we determined the ground truth of the sizes and positions through careful manual operations. We compared the size and position results detected by each method through the ground truth of the elemental images. The ground truth is set by hand to determine the exact size and position. For the ground truth size, we manually counted the number of lenses in the picked-up image. Then four corner points are also manually determined by careful visual inspection of the raw image. The number and four corner points yield the size of the elemental image by dividing the distances of corner points by the number. Moreover, the ground truth positions can be determined from the positions of the counted segment lines between corner points. Table 1 and Figure 7 show the experimental results in terms of accuracy. Table 1 says that some poor results can be made from the existing method, especially the diagonal pattern object. The size error is 6.43 pixels for this object image, compared with the ground truth. The strong edges inside of elemental images from the diagonal pattern affect the projection profiles. However, our method improved the existing extraction method by adding our postprocessing technique so that the size error is improved to 0.29 pixels. Thus, the poor results of the existing method were converted to acceptable results with high  
Figure 5: Histograms of horizontal scanning results. accuracy, as shown in Figure 7a. Here, the ground truth is highlighted in green, the grid extracted by the existing method is in blue, and the grid is in red for the proposed method. Similarly, for the car and bear and ruler images, the element image size errors from the existing method are 1.38 and 1.20, respectively. Moreover, the left images of Figure 7b,c shows the moderate results of the existing method. However, the position errors cannot be acceptable since their averages of position errors are 7.37 and 10.10, respectively. On the other hand, the proposed processing method turned the averages of position errors into 1.87 and 2.86, respectively, which are much smaller than the existing method. Moreover, Figure 7b,c depicted this improvement of our method visually. Figure 8 shows the detected area of the lens array to bound EIA. In the experimental images, some regions are not in the lens array area. These regions should be discarded in detected EIA. The proposed method for a lens array area provides acceptable results according to Figure 8 which shows three resulting images from the detection of the lens array areas. Here, the detected EIA area is highlighted in the red box. The zoomed areas in Figure 8 clearly show the performance of the lens array area detection. These results also indicate our method is very effective in taking elemental images maximally.