Hideaki HANEISHI,¹ Ritsuko OHTAKE,¹ Norimichi TSUMURA,¹ Yoichi MIYAKE,¹ Po-Chie HUNG,² Hans ROEHRIG³ and William J. DALLAS³

¹Department of Information and Image Sciences, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba, 263-8522 Japan, ²R&D Center, Konica Corporation, No. 1 Sakura-machi, Hino, Tokyo, 191 Japan, ³Department of Radiology, The University of Arizona, Tucson, AZ 85704, USA

(Received January 22, 1998; Accepted April 9, 1998)

A method is presented for matching apparent sharpness between digital image display devices with different characteristics. The sharpness is most precisely described by the point spread function (PSF) as opposed to dot density such as DPI (dot per inch). The difference between devices is expressed as difference between transfer functions obtained from the PSFs. In the presented method, spatial frequency filtering for one digital image is carried out where the ratio of the transfer functions or its modified version is used as filter. The modification is introduced as a clipping operation to reduce excessive enhancement when the ratio of the transfer functions has a high pass characteristic with large gain. Through computer simulation including a subjective evaluation experiment and numerical evaluation, the effectiveness of filtering operation for sharpness matching is demonstrated.

Key words : sharpness matching, modulation transfer function, point spread function, computer simulation, CRT, film recorder

haneishi@ics.tj.chiba-u.ac.jp