To address this issue, Toshiba has developed an AI technology that can easily measure the sizes of areas to be repaired by using several photos taken from a distance by a monocular camera, even in high places, inclinations, and other situations where inspections are difficult (Figure 2).
The developed AI is the world’s first technology that does not require gyroscope or reference information regarding sizes, as have been required in the past, and can perform actual-scale 3D measurements even from imaging distances that have not been pretrained.
The developed AI is characterized in that, by combining blur information contained in captured images with relative depth information obtained from multiple imaging positions (multi-viewpoint images), it can measure absolute sizes using only a monocular camera. Because depth information obtained from multi-view images is obtained as relative values, it has been necessary to provide a separate gyroscope that gives absolute values and information about them. Furthermore, size measurements from blur information require a camera parameter called focal length, which conventionally requires pretraining.
Toshiba recently discovered that absolute size values can be obtained using only acquired images by solving optimization problems in which depth information obtained from multi-view images and blur information of captured images are used as inputs, and scale information and focal length are set as unknown parameters (Figure 2). Applying this AI to crack measurement, Toshiba confirmed that it can accurately measure crack sizes from a distance of 7 m, which is difficult to do with technologies for size measurements using smartphones due to the large error involved (Figure 3). Measuring object sizes from distances of 5–7 m at 11 outdoor locations, they found that the size error was 2.5% under ideal conditions with a fixed lens, and restrained to 3.8% even under more difficult conditions with a zoom lens (Figure 4). Numerical simulations (assuming that cracks can be accurately detected in images) based on concrete crack repair guidelines established by the Japan Concrete Institute confirmed this accuracy and also that the necessity of repair can be determined with high accuracy (Figure 5). Toshiba also confirmed the possibility of measuring the absolute sizes of fine cracks with widths of less than 2 mm (Figure 6), and of obtaining reasonable measurements for cracks in high walls (Figure 7), which had previously been difficult.