| 摘要 |
PROBLEM TO BE SOLVED: To visibly indicate the shade of a halftone image such as a picture or a character. SOLUTION: A plurality of pit 1 is spirally formed in a random pattern. A ratio between the length of the pit 1 and that of the land 2 in a dummy pit string is varied in accordance with the shade of a picture or a character. As a result, a visual difference in contrast is produced by the distribution of such ratio, thereby making plural gradations visible of a halftone image such as a picture or a character. A part in which the length of the pit 1 is small in the ratio to the land 2 becomes a light shade part 3 of the picture or the character, while a part in which the length of the pit 1 is large in the ratio becomes a dark shade part 5 of the picture or the character. |
