MOVING IMAGE BINARY-CODING DEVICE

PURPOSE:To code a time-series image into binary data continuously by adding differential binary image data and digital binary image data and thus finding target binary image data, predicting an area to be coded into binary data in a next field,and determining a proper binary-coding threshold value. CONSTITUTION:The target binary image data 49 in some field is found by adding the differential binary image data 90 and digital binary image data 43 together and a target predicting circuit 51 predicts the area to be coded into binary data in the next field by using enlargement rate data 50 and the target digital binary data 49. Occupation rate data 22 on the differential binary image data 88 and occupation rate data 45 on binary image data 36 in the limited area are used to determine proper binary-coding threshold values 87 and 33 even when the differential image histogram and higher harmonic image histogram 30 of the limited area do not have double hump responses. Consequently, only the target area can be coded into binary data stably and effectively.