3D measurement with active triangulation for spectacle lens optimization and individualization

We present for the first time an active triangulation technique for video centration. This technique requires less manual selection than current methods and thus enables faster measurements while providing the same resolution. The suitability to measure physiological parameters is demonstrated in a measurement series. The active triangulation technique uses a laser line for illumination which is positioned such that it intersects with the pupils of the subject to be measured. For the illumination of human eyes, the wavelength and output power were carefully investigated to ensure photobiological safety at all times and reduce irritation of the subject being measured. A camera with a known orientation to the laser line images the subject. Physiological features on the subject and the frame are then selected in the acquired image yielding directly a 3D position if lying on the illuminated laser line. Distances to points off the laser line can be estimated from a scaling at the same depth. Focus is on two parameters: interpupillary distance (PD) and corneal face form angle (FFA). In our study we examined the repeatability of the measurements. We found an excellent repeatability with small deviations to the reference value. Furthermore a physiological study was carried out with the setup showing the applicability of this method for video centration measurements. A comparison to a reference measurement system shows only small differences.