NED Lenses with Liquid Lens Focus for AR/VR/MR Display Testing

In this work, we present a compact single-device solution for optical characterization of AR projectors and near-eye display (NED) systems. Our system combines an imaging luminance measurement device (ILMD) with Type II calibration and a liquid lens-based NED front stop lens. Type II calibration provides photometric calibration and geometric mapping between sensor pixels, viewing directions, and object distances. The liquid lens enables a short minimal focus distance to past infinity with constant image quality and no entrance pupil shift across the entire focus range. This allows us to realize a compact photometric measurement setup including a rapid alignment method. It works through focus-based distance measurements of the eyebox or exit pupil of AR devices or components. Experimental validation shows significant time savings compared to standardized eyebox scanning approaches, while maintaining similar positioning accuracy.

A spectroscopic measurement should reference color measurement parameters for high - precision color measurements using an imaging color measuring device (ICMD) . Within an augmented and virtual reality (AR/VR, in general, called near-eye displays - NED) measurement application, the spectral distribution of the device under test (DUT) should be measured within a 2° field of view according to the standard observer. The measuring spot should be on the optical axis of the imaging device. Integrating the spectrometer coupling in an AR/VR measuring lens can guarantee those fundamental criteria by optical design and adjustment. We present a lens design that meets these requirements and thus combines other various advantages of the elemental lens design.

As head-up displays play an increasingly important role in modern vehicle cockpits, there is a growing demand for measurement procedures to characterize them. There are two general approaches to measuring virtual image distance, a parallax-based triangulation method and a focus-based technique. They can be performed using Imaging Luminance Measurement Devices with type II calibration, making them suitable for photometrical and geometrical measurements. This paper examines the advantages and drawbacks of both methods using mathematical models and measurement data.

More and more, the suppliers of near-to-eye displays (NED) are seeking cost-effective imaging luminance and color measurement solutions that are adaptable to their instrument structures. Here, the authors offer a set of formulas that determine the basic parameters of imaging luminance and radiance measurement devices and lenses for different NED-concepts.

This contribution aims to describe the challenges associated with the characterization of NED (Near-Eye Displays) using Imaging Luminance and Color Measuring Devices. Based on the special attributes of NED systems, the requirements for the measurement set-up are deduced. Then two special lens designs, the hypercentric lens and the front stop lens, which both overcome these challenges, are introduced. This includes their concepts, applications and presentation of exemplarily obtained results.