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Viewing Cone measurement - 16 Pages

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Viewing Cone measurement

Catalog excerpts


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Viewing Cone Series High performance Fourier Optics viewing angle instrument ELDIM has been manufacturing viewing angle instruments based on Fourier optics for more than 15 years. One of their key features is the patented optical configuration which allows controlling the angular aperture of the system independently of the measurement spot size. Extreme grazing angles (88°) are measured with an excellent accuracy thanks to a very high light collection efficiency . High Speed The full viewing cone is measured with high incidence and azimuth angular resolution within seconds for luminance and...

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Viewing Cone Series Comparison to other techniques Viewing angle properties are certainly among the most common characteristics measured on any type of displays. Historically, goniometers were the first equipments used to perform angular measurements. Main drawback of those systems is the “one after each other” nature of the measurements which results in very long acquisition times if more than a few directions are required. ELDIM has introduced Fourier optics instruments in 1993(*). A specific optic is designed in order to convert angular field map into a planar one allowing very rapid...

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Viewing Cone Series Fourier Ictu direction Fourier plane Principle of Fourier optics How to calculate the illumination on the Fourier plane Optical uciE Schematic diagram of a standard Fourier optics Spot size changes with the incidence for goniometer-based systems Fourier Optics Trends Collection efficiency A Fourier optic is simply a lens (or a collection of lenses) that collects the light emitted by a small surface and refocus rays of light on a plane -called the Fourier plane- at a position that depends on their incidence and azimuth angles. The illumination of an elemental surface on...

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Viewing Cone Series The efficiency of the system becomes less sensitive to the incidence angle than previously as shown in the figure. Nevertheless it is always going down to zero for grazing incidences and this optical design remains therefore inefficient at incidence angles higher than 60-70°. The coverage of a wide angular range requires to further combine this Fourier optic with another optical setup. Fourier optics with cosine compensation This configuration has been patented by ELDIM (*).The Fourier optics plane is imaged onto the detector using a field lens and an imaging lens. An...

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Viewing Cone Series Working Distance Spots on DUT Impact of the distance on the light collection with Fourier optics instrument: at optimum working distance OWD all the angles are measured at the same location (top); if the distance is higher than OWD all the angles are not measured at same location (bottom). Impact of working distance An ELDIM Fourier optics system has an optimal working distance in the range of 1 to 4mm depending on its angular aperture. In contradiction with what is generally thought, this working distance is not critical since the system is collecting “plane waves” at...

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Viewing Cone Series How to achieve a large spot size with Fourier instrument Achieving simultaneously a wide angular aperture and a large spot size is a technical challenge. The main constraint lays into the conservation of the geometric étendue. This general principle is the consequence of the energy conservation and can be expressed as: Ss and Sd are respectively the surfaces of the source and the detector, and Ωs and Ωd the solide angles of the light on the source and on the detector. If we need at the same time a large spot size on the source and a high angular aperture, a very big...

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Viewing Cone Series Polarization measurement on OFF state on LCD (left), cross section in polar (middle) and on Poincare sphere (right)

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Viewing Cone Series Horizontal azimuth Vertical azimuth Horizontal azimuth Vertical azimuth Luminance versus grey level and incidence angle along 0°(left) and 90°(right) azimuths normalized lightness versus grey level and incidence angle along 0°(left) and 90°(right) Grey level analysis Although the Iso-Contrast curves are useful for LCDs displaying bi-level images, they are not suitable for LCDs displaying grey scale images.That's why a specific toolbox has been developed: the grey level analysis that allows dis- playing grey level measurements in different ways and also calculating...

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Viewing Cone Series Polarization Option Light can have different states of polarization. It can be randomly polarized (or unpolarized). This is generally the case for natural light. It can also be linearly polarized. In this case the electric field is oscillating always in the same plane. In any case the electric field characterizing any light wave can be separated into two components: Definition of elliptic parameters of polarized light The polarized component can be defined by its elliptical coefficients (ellipticity ε and orientation α) as shown hereafter. Unpolarized light component is...

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Viewing Cone Series Reflective Options In contrast with all other techniques, ELDIM Fourier optics instruments are able to illuminate the sample under test while measuring at the same angles. The illumination is made across the Fourier optics using a beam splitter and an additional focal system that reconstructs the first Fourier plane at another location perpendicular to the optical axis of the system. One point on this illumination Fourier plane corresponds to one angle on the sample. Two illumination options are available that correspond to different illumination modes. Optical layout of...

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Viewing Cone Series Reflection components for collimated beam illumination Collimated beam reflective option The illumination is made with a small optical filter located on the Fourier illumination plane and a white light source with filters. This location which corresponds to the incident angles on the sample can be controlled manually or automatically. Full reflective pattern of the sample is measured in one measurement. Specular, haze and Lambertian contributions are measured simultaneously. Multi-exposures can be performed to enhance the dynamic. Front glass reflection Interest of...

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All ELDIM catalogs and technical brochures

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