Due to the booming in LED applications, fast and accurate inspection tools to monitor LED quality is necessary. In this
paper, we propose two new methods to measure LED optical properties by using imaging spectrograph. Imaging-type
spectrograph with high spatial and spectral resolutions is designed for LED wafer measurement. Fiber-type spectrograph
with multi-head structure is designed for LED backlight and LED light-bar measurement. Optical properties of LED
include chromaticity and luminous intensity, which are measured by following CIE recommendations. The performance
of imaging spectrograph is evaluated to meet industrial requirements for LED measurement.
We propose a novel multi-channel liquid crystal cell parameter measurement system, which combines the spectroscopic
ellipsometry technique with the hyperspectral imaging spectrograph for the multi-point measurement. This system is
based on PSA setup (polarizer-sample-analyzer) to measure normalized transmission spectrum for analyzing properties
of homogeneous cell and MVA cell. We also develop a theoretical method to simplify the calculation of the orientation
angle of liquid crystal cells for speeding up the measurement. The liquid crystal cell gap can be calculated by the
measured retardation and the given refractive indices of specified wavelength. The pretilt angle is also analyzed by
multi-channel measurement system. We present the analysis of hyperspectral imaging spectrograph and the orientation
angle measurement by direct calculation method for high speed on-line multi-channel liquid crystal cell parameter
The ellipsometric image contrast for patterned film in whole visible range is simulated and analyzed in this article. By the Fresnel equation and the Jones Matrix, the characteristic wavelength selection method to enhance the image contrast is built. The ellipsometric reflected intensity of specific thin film is nulled into dark by rotating the phase angle of compensator and the azimuth angle of polarizer in whole visible range, which results in higher contrast between non-null and null images after the proper wavelength selection. The approach enables the image defect recognition of patterned film more obvious than recent single wavelength imaging ellipsometry and white light reflective image.
We propose a novel grating-based all-transmissive imaging spectrograph in which the collimating and focusing optics have the same optical structure with a linear chromatic dispersion and the minimized Seidel aberrations. The imaging spectrograph is designed as a telecentric system on both object and image side. The spectral and spatial resolutions of the imaging spectrograph can be improved. A designed and an achromatic lens type are compared for demonstrating the performance.