1611 原著 論文受付 2009 年 6 月 2 日 論文受理 2009 年 9 月 18 日 Code No. 733 ピクセル開口率の向上による医用画像表示用カラー液晶モニタの物理特性の変化 澤田道人 石川晃則 1) 松永沙代子 1) 1) 石川陽子 有限会社ムツダ商会 1) 安城更生病院放射線技術科 緒言 3D PET/CT Fusion 1 liquid crystal display: LCD LCD LCD Influence on the Physical Characteristics of Medical Color Liquid Crystal Displays with Increase in Aperture Ratio Michito Sawada, Akinori Ishikawa, 1) Sayoko Matsunaga, 1) and Yoko Ishikawa 1) Mutsuda Shoukai Corporation, Ltd. 1)Department of Radiology, Anjo Kosei Hospital Received June 2, 2009; Revision accepted September 18, 2009; Code No. 733 Summary We measured the physical characteristics of 2-million 2M and 3-million 3M color liquid crystal displays LCD whose aperture ratio was increased and compared them with conventional models. The results showed the influence of the increased aperture ratio on the physical characteristics of the LCDs. We evaluated resolution by means of modulation transfer function MTF and evaluated granularity by means of noise power spectrum NPS. Each of the measurements was done with a high-resolution single-lens reflex-type digital camera. A decrease of MTF depending on sub-pixel structures was recognized. A decrease in the cross sub-pixel direction was recognized in the 2M model, and a decrease in the sub-pixel direction was recognized in the 3M model. As for NPS, a reduction was recognized in the sub-pixel and the cross sub-pixel direction in both models. As a result, an improvement in granularity was recognized. The improvement in granularity was large with the color LCDs whose aperture ratio was increased. The increase of an aperture ratio influenced both MTF and NPS, and the results depended on the shape and size of the sub-pixel cells. Key words: liquid crystal display (LCD), modulation transfer function (MTF), noise power spectrum (NPS), aperture ratio, sub-pixel 462-0845 4 5 16
1612 Table 1 Specifications of the monitors used RX210 RX211 R31 RX320 Active Display Size mm 324 432 324 432 318 423.9 323.7 431.6 Native Resolution 1200 1600 1200 1600 1536 2048 1536 2048 Pixel Pitch mm 0.27 0.27 0.207 0.21075 Luminance cd/m 2 600 750 400 900 Recommended Luminance cd/m 2 240 300 250 400 Contrast Ratio 600 1 1100 1 400 1 1000 1 Table 2 Calibration setting and measured luminance Luminance Setting 1 Maximum Minimum Color Luminance Luminance Temperature Measured Luminance at input level 128/255 cd/m 2 cd/m 2 K cd/m 2 RX210 240 0.7 7500 30.43 RX211 240 0.7 7500 30.51 R31 250 0.9 8000 32.61 RX320 250 0.9 8000 32.93 Luminance Setting 2 Maximum Minimum Color Luminance Luminance Temperature Measured Luminance at input level 128/255 cd/m 2 cd/m 2 K cd/m 2 RX211 300 0.5 7500 33.37 RX320 400 0.7 8000 42.65 1, 2 LCD modulation transfer function MTF noise power spectrum NPS 1. 方法 LCD 2-million 2M model RX211 3-million 3M model RX320 model 2M RX210 3M R31 LCD Table 1 LCDmodel / 100 / 100 Fig. 1. MTF NPS 3 7 Nikon Micro-Nikkor 60mm f/2.8d Nikon D70 3040 2014 1 12bit LCD Digital Imaging and Communications in Medicine DICOM Part14 Grayscale Standard Display Function GSDF MTF Table 2 65 12
1613 Fig. 1 Sub-pixels contained in each pixel element. Fig. 2 Comparison of MTF of the current sub-pixel model RX210 and MTF of the improved sub-pixel model RX211. a-1 sub-pixel direction a-2 cross sub-pixel direction 1 Table 2-1 NPS Table 2-1 Table 2 2 Table 2-2 RadiCS 2. 結果 Fig. 1 100 model model 2M 3M 2M model 3M model model 2M 31.3 48.0 3M 35.1 55.2 2M 136 121 3M 140 134 Fig. 2 2M MTF a-1 a-2 0.9 1.852cycles/mm 2.4 5.6 MTF 3M MTF Fig. 3 b-1 1.2 2.372cycles/mm
1614 Fig. 3 Comparison of MTF of the current sub-pixel model R31 and MTF of the improved sub-pixel model RX320. b-1 sub-pixel direction b-2 cross sub-pixel direction Fig. 4 Comparison of NPS of the current sub-pixel model RX210 and NPS of the improved sub-pixel model RX211. Setting 240 cd/m 2 of the luminance. a-1 sub-pixel direction a-2 cross sub-pixel direction 2.7 10.7 MTF b-2 2M 3M model MTF 2M 3M MTF 3M Fig. 4 2M model NPS model Table 2-1 NPS a-1 3.7cycles/mm 0.27mm 1/0.27=3.72M model NPS 3M model Fig. 5 2M Table 2-1 3M model NPS 2M 3M model 65 12
1615 Fig. 5 Comparison of NPS of the current sub-pixel model R31 and NPS of the improved sub-pixel model RX320. Setting 250 cd/m 2 of the luminance. b-1 sub-pixel direction b-2 cross sub-pixel direction NPS Table 2-2 2M 3M Table 2-1 Fig. 6 7 model NPS 3. 考察 Fig. 1 2M 3M model LCD model 2M 1.53 3M 1.57 IPS 2M 3M Table 1 2M model 3M model MTF MTF 2M MTF Fig. 2 a-2 Fig. 1 2M MTF Fig. 2 a-1 3M 2M MTF Fig. 3 b-1 Fig. 3 b-2 NPS Fig. 4 5 2M 3M model NPS 2M 3M model
1616 Fig. 6 Comparison of NPS with setting luminance 240 cd/m 2 in improved sub-pixel model RX211 and setting luminance 300 cd/m 2. a-1 sub-pixel direction a-2 cross sub-pixel direction Fig. 7 Comparison of NPS with setting luminance 250 cd/m 2 in improved sub-pixel model RX320 and setting luminance 400 cd/m 2. b-1 sub-pixel direction b-2 cross sub-pixel direction 3M model 65 12
1617 Fig. 6 7 2M 3M Table 2-2 NPS Table 2-1 model NPS NPS NPS 4. 結語 LCD model LCD LCD 参考文献 1 4 Innervision 2006 21 6 70-74 2 2006 29 2 11-16 3 Ichikawa K, Fujita H, Sawada M. Novel MTF measurement method for medical image viewers using a bar pattern image. Proc. SPIE 2003; 5029: 624-631. 4 MTF 2004 67 2 184-190 5 2004 21 3 261-266 6 Ichikawa K, Kodera Y, Fujita H. MTF measurement method for medical displays by using a bar-pattern image. Journal of the Society for Information Display 2006; 14 10 : 831-837. 7 Ichikawa K, Horii A, Kodera Y. Novel NPS measurement method for medical liquid crystal display using periodic components subtraction technique. Proc. SPIE 2006; 6142, 61423H: 1-8. 図表の説明 Fig. 1 Fig. 2 RX210 RX211 MTF a-1 a-2 Fig. 3 R31 RX320 MTF b-1 b-2 Fig. 4 RX210 RX211 NPS 240cd/m 2 a-1 a-2 Fig. 5 R31 RX320 NPS 250cd/m 2 b-1 b-2 Fig. 6 RX211 240cd/m 2 300cd/m 2 NPS a-1 a-2 Fig. 7 RX320 250cd/m 2 400cd/m 2 NPS b-1 b-2 Table 1 Table 2