Woestenburg J C, Verbaten M N, Slangen J L
Biol Psychol. 1984 Mar;18(2):149-60. doi: 10.1016/0301-0511(84)90017-6.
A method for calibration, orthogonalization and standardization of eye movements is described. The method is based on linear transformation of the horizontal and vertical EOG. With this method it is possible to measure the locus of eye fixation on a TV screen and its associated fixation time. Because of the used time constant (TC) of 36 sec, subjects must look at the centre of the TV screen or at random places on the screen during the interstimulus intervals (ISIs). For the EOG registration pre-amplifiers with a long TC were used to cut off slow changes in polarization caused by the electrode-electrolyte combination. In the calibration procedure only four orthogonal stimulus points were used. In an experiment to evaluate this method, subjects had to fixate letters on a TV screen in 12 different pre-determined positions. The distance between the measured locus of fixation and the coordinates of the stimulus was measured. The mean horizontal errors ranged from 1.4-2.2 degrees of arc and the mean vertical errors from 2.4-3.8 degrees of arc across subjects. It was concluded that accuracy was within acceptable limits, despite the fact that eye movement behaviour during the ISI was free. It was shown that the method is insensitive to non-orthogonality of the vertical and horizontal EOG. Calibration and transformation can be done by any real time computer system. The method is suitable for measuring, e.g. the visual orienting reaction (VOR), and it can also be applied in event related potential (ERP) studies where ocular fixation is used.
本文描述了一种用于眼动校准、正交化和标准化的方法。该方法基于水平和垂直眼电图（EOG）的线性变换。使用这种方法，可以测量电视屏幕上的眼注视位置及其相关的注视时间。由于使用了36秒的时间常数（TC），在刺激间隔（ISI）期间，受试者必须注视电视屏幕的中心或屏幕上的随机位置。对于EOG记录，使用了具有长TC的前置放大器来消除由电极-电解质组合引起的极化缓慢变化。在校准过程中，仅使用了四个正交刺激点。在一项评估该方法的实验中，受试者必须在电视屏幕上12个预先确定的不同位置注视字母。测量了注视的测量位置与刺激坐标之间的距离。受试者的平均水平误差范围为1.4 - 2.2度弧度，平均垂直误差范围为2.4 - 3.8度弧度。得出的结论是，尽管ISI期间的眼动行为是自由的，但准确性仍在可接受范围内。结果表明，该方法对垂直和水平EOG的非正交性不敏感。校准和变换可以由任何实时计算机系统完成。该方法适用于测量，例如视觉定向反应（VOR），也可应用于使用眼注视的事件相关电位（ERP）研究。
