Katsuhiro Ichikawa PhD, Presenter: License agreement, Totoku Electric Co, Ltd Research support, Totoku Electric Co, Ltd

Mikio Hasegawa, Abstract Co-Author: Employee, Totoku Electric Co, Ltd

Naohiro Kimura, Abstract Co-Author: Nothing to Disclose

Yutaka Tanaka, Abstract Co-Author: Nothing to Disclose

Recently, color liquid crystal displays (LCDs) are becoming more popular than monochrome LCDs because of their availability to display color information. However, many radiologists point out that color LCDs is somewhat inferior to monochrome LCDs to interpret monochrome images. Contrary to these doctors’ indications, there have been few reports to describe the detailed difference of image quality between color and monochrome LCDs. As a cost effective monochrome LCD, we have developed a 6 mega-sub-pixel (MsP) monochrome LCD (6MsP-mLCD) out of a 2MP monochrome LCD, using the independent sub-pixel driving (ISD) technology, and reported its better performances. This 6MsP-mLCD costs almost the same as the 2MP color LCDs (2MP-cLCD). In this study, we compared physical performances and perceptual detectability of low-contrast objects for monochrome image displaying between the 2MP-cLCD and the 6MsP-mLCD.  

We compared the two LCDs by means of the following methods; - Modulation transfer function (MTF) as a resolution index - Noise power spectrum (NPS) as a noise property index - Low contrast detection study by five radiological technologists, using low-contrast objects displayed at a random position within the specific region. The MTFs of the two LCDs were almost equivalent. On the other hand, the NPS of the 2MP-cLD was remarkably inferior to that of 6MsP-mLCD. The detectability of the 2MP-cLCD and the 6MsP-mLCD for one of the low-contrast objects were 95.3% and 10.8% respectively, and there was great difference between them.  

A single pixel on a color LCD is made of three colored elements called RGB sub-pixels. We considered that this complex pixel structure caused the inferior performance demonstrated in this study. The results of the detectability study we performed clearly indicated the inferiority of the 2MP-cLCD, which was supported by the NPS results and verified the doctors’ indications.

It was indicated that the 2MP-cLCD had not enough performance to display monochrome images due to its noise components caused by the RGB sub-pixel structure. In contrast, the 6MsP-mLCD was more advantageous due to both its enhanced resolution and noise properties.

Ichikawa, K, Hasegawa, M, Kimura, N, Tanaka, Y, Usefulness of 6 Mega-Sub-Pixel Monochrome LCDs Comparing with 2 Mega-Pixel Color LCDs.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8011016.html