Low cost and compact 3D imaging for various applications like face-recognition, machine vision or LIDAR for automotive has introduced new requirements in terms of NIR light source characterization. These sources must comply safety regulations and must be verified rapidly and accurately during the fabrication process. In addition, precise characterization of the light source emissions within their entire angular aperture is mandatory to get accurate 3D images. The paper introduces a new Fourier optics system dedicated to this task.
We explain the technical bases of the Fourier Optics Technology (OFT) for viewing angle measurement of displays and the increasing capacities of the ELDIM systems over the years. A new generation of OFT systems devoted to quality control is introduced. In spite of a more compact size, the optic shows excellent performances in terms of angular aperture, angular resolution and collection efficiency. The detection is made with a new generation high resolution CMOS camera which allows very short measurement times. In addition, the probe can be used on a robotic arm to offer a cost effective solution for quality control of displays with any kind of size and shape.
Different aspects of the characterization of curved displays are presented. The limit of validity of viewing angle measurements without angular distortion on such displays using goniometer or Fourier optics viewing angle instrument is given. If the condition cannot be fulfilled the measurement can be corrected using a general angular distortion formula as demonstrated experimentally using a Samsung Galaxy S6 edge phone display. The reflective properties of the display are characterized by measuring the spectral BRDF using a multispectral Fourier optics viewing angle system. The surface of a curved OLED TV has been measured. The BDRF patterns show a mirror like behavior with and additional strong diffraction along the pixels lines and columns that affect the quality of the display when observed with parasitic lighting. These diffraction effects are very common on OLED surfaces. We finally introduce a commercial ray tracing software that can use directly the measured emissive and reflective properties of the display to make realistic simulation under any lighting environment.
A new generation of Fourier optics multispectral instruments that allow rapid full diffused or collimated beam spectral
BRDF measurements is presented. Light detection is made simultaneously at all angular locations including the
illumination direction. Backscattering effect in the fields of cosmetics and parasitic reflection of mobile displays are
reported as examples.
OLED displays exhibit luminance fluctuations and color shifts that can be sensitive to human eye in particular conditions. Using viewing angle and imaging multispectral measurements we show that color shifts are generally related to the multilayered structure of each sub-pixel. Interference fringes result in angular variations while thickness variations result in surface non-uniformities.
Different ways to evaluate the optical performances of auto-stereoscopic 3D displays are reviewed. Special attention is
paid to the crosstalk measurements that can be performed by measuring, either the precise angular emission at one or few
locations on the display surface, or the full display surface emission from very specific locations in front of the display.
Using measurements made in the two ways with different instruments on different auto-stereoscopic displays, we show
that measurement instruments need to match the resolution of the human eye to obtain reliable results in both cases.
Practical requirements in terms of angular resolution for viewing angle measurement instruments and in terms of spatial
resolution for imaging instruments are derived and verified on practical examples.
Optical characterization of multi-view auto-stereoscopic displays is realized using high angular resolution viewing angle measurements and imaging measurements. View to view and global qualified binocular viewing space are computed from viewing angle measurements and verified using imaging measurements. Crosstalk uniformity is also deduced and related to display imperfections.
Two commercial auto-stereoscopic 3D displays are characterized a using Fourier optics viewing angle system and an
imaging video-luminance-meter. One display has a fixed emissive configuration and the other adapts its emission to the
observer position using head tracking. For a fixed emissive condition, three viewing angle measurements are performed
at three positions (center, right and left). Qualified monocular and binocular viewing spaces in front of the display are
deduced as well as the best working distance. The imaging system is then positioned at this working distance and
crosstalk homogeneity on the entire surface of the display is measured. We show that the crosstalk is generally not
optimized on all the surface of the display. Display aspect simulation using viewing angle measurements allows
understanding better the origin of those crosstalk variations. Local imperfections like scratches and marks generally
increase drastically the crosstalk, demonstrating that cleanliness requirements for this type of display are quite critical.
All 3D displays have the same intrinsic method to induce depth perception. They provide different images in the left and
right eye of the observer to obtain the stereoscopic effect. The three most common solutions already available on the
market are active glass, passive glass and auto-stereoscopic 3D displays. The three types of displays are based on
different physical principle (polarization, time selection or spatial emission) and consequently require different
measurement instruments and techniques. In the proposed paper, we present some of these solutions and the technical
characteristics that can be obtained to compare the displays. We show in particular that local and global measurements
can be made in the three cases to access to different characteristics. We also discuss the new technologies currently under
development and their needs in terms of optical characterization.
A method to characterize time sequential stereoscopic 3D displays which is based on the measurement of the
temporal behavior of the system versus grey levels is presented. OPTISCOPE SA, especially designed for precise
measurement of luminance and temporal behavior of LCD displays is used. The transmittance and response time of
the shutter glasses is first evaluated. Then the grey to grey response times of the display alone are measured. Finally,
the temporal behavior of the complete system is modeled and grey to grey crosstalks are deduced. Resulting
luminance on left and right eyes of the observer are deduced and compared to integrated measurements using a
spectrophotometer. Quality control method using grey level test patterns and imaging luminance meter is deduced
and applied to different types of commercial 3D TVs.
In this paper we propose a method to characterize polarization based stereoscopic 3D displays using multispectral
Fourier optics viewing angle measurements. Full polarization analysis of the light emitted by the display in the full
viewing cone is made at 31 wavelengths in the visible range. Vertical modulation of the polarization state is observed
and explained by the position of the phase shift filter into the display structure. In addition, strong spectral dependence of
the ellipticity and polarization degree is observed. These features come from the strong spectral dependence of the phase
shift film and introduce some imperfections (color shifts and reduced contrast). Using the measured transmission
properties of the two glasses filters, the resulting luminance across each filter is computed for left and right eye views.
Monocular contrast for each eye and binocular contrasts are performed in the observer space, and Qualified Monocular
and Binocular Viewing Spaces (QMVS and QBVS) can be deduced in the same way as auto-stereoscopic 3D displays
allowing direct comparison of the performances.
In this paper we apply imaging polarimetry to characterize polarization based stereoscopic 3D displays. New imaging
polarimeter is first described and its potentialities to characterize LCDs and their components are shown. Then one
polarization based stereoscopic 3D display is measured with this new tool. 3D and standard contrast are evaluated on the
entire surface of the display and compared to what is expected from viewing angle measurements at specific locations.
Important inhomogeneities probably related to the quality of the phase shift film are detected. Color shifts are measured
and interpreted with regards to polarization multispectral viewing angle measurements. The main sources of
imperfections are detected and solutions to improve the characteristics are proposed.
KEYWORDS: 3D displays, 3D metrology, Eye, Spatial resolution, Fourier optics, 3D vision, 3D imaging standards, Image quality standards, Sensors, Standards development
Auto-stereoscopic 3D displays offer presently the most attractive solution for entertainment and media consumption.
Despite many studies devoted to this type of technology, efficient characterization methods are still missing. We present
here an innovative optical method based on high angular resolution viewing angle measurements with Fourier optics
instrument. This type of instrument allows measuring the full viewing angle aperture of the display very rapidly and
accurately. The system used in the study presents a very high angular resolution below 0.04 degree which is mandatory
for this type of characterization. We can predict from the luminance or color viewing angle measurements of the
different views of the 3D display what will be seen by an observer at any position in front of the display. Quality criteria
are derived both for 3D and standard properties at any observer position and Qualified Stereo Viewing Space (QSVS) is
determined. The use of viewing angle measurements at different locations on the display surface during the observer
computation gives more realistic estimation of QSVS and ensures its validity for the entire display surface. Optimum
viewing position, viewing freedom, color shifts and standard parameters are also quantified. Simulation of the moire
issues can be made leading to a better understanding of their origin.
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