Katsuhiro Ichikawa PhD, Presenter: Nothing to Disclose

Mikio Hasegawa, Abstract Co-Author: Nothing to Disclose

Yutaka Tanaka, Abstract Co-Author: Nothing to Disclose

In the guidelines for display's quality assurance of American Association of Physicists in Medicine (AAPM), acceptance levels of luminance and chromaticity uniformity are specified. However, since the number of measuring points is only five and we can easily recognize visual un-uniformity even on displays with acceptable levels of Δu'v' <0.01. Therefore, we considered that further improvement of the gray-scale chromaticity uniformity (GSCU) is not meaningless for more precise gray-scale image displaying on color displays. The purpose of this study was to investigate a simple method to improve the GSCU utilizing a commercial digital camera.

We employed a commercial digital camera, Nikon D90, equipped with a micro lens for measuring the luminance and chromaticity. Grayscale full screen test patterns with 100 and 200 digital drive levels (DDLs) were displayed on a color display (ME253i2, TOTOKU) calibrated at a maximum luminance of 300cd/m2. Displaying the patterns, the luminance and chromaticity at 20 (4 x 5 ) points on the screen were measured by using a chromaticity meter (CA-110, KonicaMinolta), and then the patterns were imaged by D90. The chromaticity and luminance values for 48 points covering whole screen area was measured from raw data of the camera, and then RGB correction maps for compensating the GSCU were generated. Displaying the test patterns applied the maps, the chromaticity and luminance at 20 points were measured.

Before the correction, the Δu'v' and maximum luminance deviations were 0.0062; 11.2% for 100-DDL and 0.0058; 10.5% for 200-DDL, respectively. After the correction those were 0.00083; 5.3% and 0.00068; 4.5%. Since the color correction maps were generated in 8bit x 3 color resolution, the slight contour lines were visible on corrected test patterns. This problem will be improved by using internal 10bit look-up tables for the correction maps.

The gray-scale chromaticity uniformity correction utilizing commercial digital camera was successfully achieved at 100 and 200-DDLs. The enough possibility of chromaticity correction for all DDLs was indicated.

If the grayscale chromaticity uniformity correction, which were preliminary examined in this study, will be achieved, the performance and utility of color displays will be effectively improved.

Ichikawa, K, Hasegawa, M, Tanaka, Y, Gray-scale Chromaticity Uniformity Correction of Color Displays Utilizing Commercial Digital Camera: Preliminary Study with Limited DDL Levels.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12032626.html