| 摘要 |
PURPOSE:To increase the detecting signal, by using at least one stage of pattern just before a detector larger than other patterns among plural stage of patterns formed in the progressing direction of bubbles in a bubble expander. CONSTITUTION:As one bit 9 just before a bubble detector 5, a pattern 10 having the shape of modified double chevron patterns and a large pitch is used in comparison with other patterns having a simple chevron pattern of the said bubble expander 6. That is, when the bubble detector uses a magneto-resistance effect, the phenomenon effected with the surrounding magnetic field is used positively and one several bits of the expander just before the detector are optimized to the detector and the detection signal of bubbles is increased in comparison with a conventional system. Since the state of bubbles just before the detector passes through the expander, the bubble is expanded fully and not effected largely with the pattern of several bits just before the detector. Thus, the detection signal is increased without blocking the expansion of the bubble. |
