| 摘要 |
<p>A digital binarization circuit for image data includes a background level detecting circuit which uses a video signal as a reference input for determining the background level of an image represented by the video signal, and outputs the background level as a first address signal. A character level detecting circuit compares the video signal with a character level in a load decision comparator and loads the video signal as a character level when the signal is less than the reference level, and outputs the character level as a second address signal. A memory circuit ouputs a threshold value stored at an address designated by the first and second address signals to a comparator. The optimum threshold value is outputted among prescribed threshold values stored in the memory circuit. The comparator compares the digitized video signal with the optimum threshold value and outputs a binary signal corresponding to the comparison result. Even for original documents with a dark background, noise is not liable to occur in the transmitted video signal, and a light character can appear clearly on the transmitted video signal.</p> |
