| 摘要 |
PURPOSE:To obtain a substantially constant binarization image even when the brightness of an object is changed by deciding a binarization level based on a signal level from a predetermined relation so as to obtain the substantially constant binarization image irrespective of the fluctuation of the signal level. CONSTITUTION:The image signal level LP of a picture signal SP outputted from a TV camera 14 is detected to obtain a deviation between the picture signal level LP and a predetermined object signal level LM, and the binarization level L is decided based on the deviation so as to obtain the constant binarization image even when the image signal level LP is fluctuated. Thereby, even when the signal level LP of the image signal SP is fluctuated according to the change of an externally entering light, the change with the elapse of a time of an illumination intensity by an illuminating device or the change of the reflection factor of the object 10. The binarization level L is changed according to the fluctuation, and the constant binarization image is always obtained without receiving the influence of the brightness of the object 10.
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