An engaging head implemented in a movement converting mechanism to engage with a screwed rod comprises an attachment body, a gear part, and a resilient pre-loading element. The fixture includes first and second mounting grips for holding opposite ends of a test specimen. In operation, the AC voltage is detected when it crosses from a negative polarity to a positive polarity, or vice versa. The method also comprises forming a conductive contact to the first semiconductor region and forming a conductive contact to the second semiconductor region. In certain example embodiments, the sealant may be a thermoplastic sealant. Then the apparatus extracts a pixel value at a boundary between a predetermined region and another region of the objective image in accordance with the approximation.