Ergonomic evaluation of a field-sequential colour projection system Sang-Hyun Kim a,b, * , Takashi Shibata a,b , Takashi Kawai a , Kazuhiko Ukai b a Graduate School of Global Information and Telecommunication Studies, Waseda University, 1011 Okuboyama, Nishi-Tomida, Honjo-shi, Saitama 367-0035, Japan b School of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan Available online 1 October 2007 Abstract A field-sequential colour projection system can display colour images using a single panel. Such a system, however, produces char- acteristic trichromatic separation, or ‘‘colour breakup’’. Colour breakup is the perceived splitting of the white portions of an image into its red, green, and blue components when the image is projected with the colour sequential method and the viewer’s eyes are moving rapidly. Viewing images containing colour breakup may cause visual fatigue and other symptoms of asthenopia. In this study, the authors examine the various subjective symptoms of asthenopia that can be caused by colour breakup. Ó 2007 Elsevier B.V. All rights reserved. Keywords: Asthenopia; Colour breakup; Colour sequential projector; Digital light processing (DLP); Ergonomic evaluation; Visual fatigue 1. Introduction Digital light processing (DLP) colour projection systems are already available and increasing their market share. DLP projectors form a binary image by means of a digital micromirror device (DMD). DLP projection systems use either a single chip or three chips to create a colour image. The cheaper and more popular DLP projectors use only a single chip. In a projector with a single chip, the colours are produced by placing a colour filter wheel between the lamp and the chip [6]. The colour filter wheel contains red, green, blue, and sometimes white (clear) filters. The wheel spins very rapidly, creating a sequence of red, green, blue, and white images that are combined into a single full colour image (Fig. 1). This technique is called ‘‘field-sequential’’. Time sequential RGB images are typically composed of one full colour image every 1/60th of a second. Although the use of a single panel can reduce both projector size and costs, the system’s field-sequential colour projection mechanism can cause the observer to perceive trichromatic separation during times of rapid eye movement [1–3]. Colour breakup is the perceived splitting of the white portions of an image into its red, green, and blue compo- nents when the image is projected with the colour sequen- tial method and the viewer’s eyes are moving rapidly. This trichromatic separation is called ‘‘colour breakup’’ (Fig. 2). Colour breakup is a phenomenon related to the mecha- nisms of human visual perception. A recent research sug- gested that colour breakup is perceived because of the imperfections in visual stability. Colour breakup affects visual fatigue in people with congenital nystagmus [4]. And this phenomenon may cause the normal viewer to feel discomfort and even visual fatigue [5]. In this study, we focused on colour breakup as a charac- teristic problem of the field-sequential colour projection system, and examined its effects as manifested through sub- jective asthenopic symptoms. 2. Experiment 1 2.1. Purpose The purpose of this experiment was to determine the characteristic symptoms of asthenopia caused by colour 0141-9382/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.displa.2007.09.008 * Corresponding author. Address: Graduate School of Global Information and Telecommunication Studies, Waseda University, 1011 Okuboyama, Nishi-Tomida, Honjo-shi, Saitama 367-0035, Japan. Tel.: +81 495 24 6076; fax: +81 495 24 6645. E-mail address: kim@akane.waseda.jp (S.-H. Kim). www.elsevier.com/locate/displa Available online at www.sciencedirect.com Displays 29 (2008) 132–137