This paper describes about the new design method for hyper-spectral Imaging spectrometers utilizing convex grating. Hyper-spectral imaging systems are power tools in the field of remote sensing. HSI systems collect at least 100 spectral bands of 10~20 nm width. Because the spectral signature is different and induced unique for each material, it should be possible to discriminate between one material and another based on difference in spectral signature of material.
I mathematically analyzed parameters for the intellectual initial design. Main concept of this is the derivative of "ring of minimum aberration without vignetting". This work is a kind of analytical design of an Offner imaging spectrometer.
Also, several experiment methods will be contrived to evaluate the performance of imaging spectrometer.
We introduce a design of an Offner imaging spectrograph with its performance and tolerancing results. It is a traditional Offner spectrograph employing two concave mirrors and one convex reflective grating for dispersing light in the SWIR band (900~1700 nm). The optical system uses 25um-pitch pixels for the detector and the goal spectral sampling is 3.2nm. Its performance is analyzed in terms of MTFs, spot diagrams, and distortions – keystone and smile. This design focuses on the yaw(beta-tilt) sensitivity of the tertiary mirror as the compensator hence is expected to act as a performance-improving breakthrough for the entire system as the inverse sensitivity confirms it is the most sensitive component. The procedure of the inverse sensitivity evaluation is explained, and then budgeting the tolerances for each element for the practical production is described.
In this paper, we propose a denoising method for hyperspectral images using a joint bilateral filter. The joint bilateral
filter with the fused image of hyperspectral image bands is applied on the noisy image bands. This fused image is a
single grayscale image that is obtained by the weighted summation of hyperspectral image bands. It retains the features
and details of each hyperspectral image band. Therefore the joint bilateral filter with the fused image is powerful in
reducing noise while preserving the characteristics of the individual spectral bands. We evaluated the performance of the
proposed noise reduction method on hyperspectral imaging systems, which we developed for visible and near-infrared
spectral regions. Experimental results show that the proposed method outperforms the conventional approaches, such as
the basic bilateral filter.
This paper presents an extended bilateral filter with spectral angles and a visualization scheme for hyperspectral image
data. The conventional bilateral filter used to be implemented using a position vector and a luminance value at each pixel
in the scene. Since hyperspectral image data can provide a spectrum vector that has hundreds of bands at each pixel, we
propose an extended bilateral filter using spectral angles. The proposed bilateral filter can be used for extracting and
preserving the spectrum edges of the hyperspectral image. A visualization scheme for hyperspectral images exploiting
the proposed bilateral filter has been also proposed. When objects that have the similar tristimulus intensity but different
spectrums are mixed, they can be separated through the proposed visualization scheme. The resulting images show that
the proposed scheme facilitates anomaly detection in the hyperspectral scenes.