Sewing machine, computer readable medium storing thread tension adjustment program for sewing machine, and thread tension evaluation unit

A non-transitory computer readable storage medium that stores a computer executable program for a sewing machine including a feed mechanism that is configured to transfer a workpiece cloth, a stitch forming mechanism that is configured to form stitches on the workpiece cloth being transferred by the feed mechanism by interlacing a needle thread and a bobbin thread, a thread tension adjustment mechanism that is configured to adjust at least either a needle thread tension applied on the needle thread and a bobbin thread tension applied on the bobbin thread, and an image capturing unit that is disposed at a position capable of capturing images of the stitches formed on the workpiece cloth and that is configured to capture images of the stitches at least from either upper and undersides of the workpiece cloth, the program, comprising:

• instructions for capturing images of the stitches at least from either upper and undersides of the workpiece cloth by the image capturing unit;
• instructions for extracting, from the image data of the stitches captured by the image capturing unit, a region of the image data, which corresponds to a portion that is occupied by an opposite side thread appearing at an interlace of the needle thread and the bobbin thread;
• instructions for calculating an area of the extracted region of the image data;
• instructions for evaluating a tension balance between the needle thread and the bobbin thread based on the area calculated;
• and
• instructions for modifying the tension balance of the stitches formed by the stitch forming mechanism through control of the thread tension adjustment mechanism based on a result of the evaluation.

A thread tension evaluation unit that evaluates tension balance of a needle thread and a bobbin thread being interlaced to form stitches on a workpiece cloth, the thread tension evaluation unit, comprising:

• an image capturing unit that captures images of the stitches at least from either upper and undersides of the workpiece cloth;
• an extracting section that extracts, from the image data of the stitches captured by the image capturing unit, a region of the image data, which corresponds to a portion that is occupied by an opposite side thread appearing at an interlace of the needle thread and the bobbin thread;
• a calculating section that calculates an area of the region of the image data extracted by the extracting section;
• an evaluating section that evaluates thread tension based on the area calculated by the calculating section;
• and
• an output unit that outputs a result of evaluation by the evaluating section.