Method of Automatic Tooth Contact Evaluation Using Near-Infrared Ray Imagery(Machine Elements, Design and Manufacturing)

Tooth contact evaluation has been conventionally performed visually by the machine operator in the gear manufacturing fields when finishing a gear or at assembly. With automation, the boundary of the contact area is unclear due to scattered light when visible light is used to obtain an image to evaluate tooth contact. We have therefore focused on the use of a near-infrared to prevent scattered light. First, a suitable wavelength is investigated to obtain a fine tooth contact image in near-infrared vision. Second, it is confirmed that the tooth contact image obtained by image binarization is hardly affected by the image threshold. Third, we propose a new method to extract the boundary part of the tooth contact by differential calculation of the fine near-infrared image. These methods make it possible to automatically divide a near-infrared image into the contact area, the boundary and the non-contact area. Finally, the obtained result is compared with the tooth contact calculated from the measured tooth surface. As a result, we demonstrated that the near-infrared image method is effective for automatic tooth contact evaluation.