An IR imaging video bolometer (IRVB) is a measurement instrument for plasma radiation with the pin-hole projection principle. The IRVB has an advantage of having a large number of detector channels. The advantage is necessary for three dimensional observation of plasma radiation with tomography techniques. The observation also requires the calculation of geometry matrices and optimization of the fields of view for the IRVB to reconstruct accurate plasma radiation distributions. In this study, fields of view for four IRVBs which were installed in LHD have been optimized by changing the aperture positions to minimize the total number of non-visible plasma-voxels in the LHD plasma. The best fields of view were chosen with the geometry matrix which is calculated as a projection matrix of the plasma radiation to the bolometer foil with an assumption of helically symmetry. There were 169 non-visible plasma-voxels which could not be measured by any of the IRVB channels in the setting before optimization. The number could be decreased to 0 by this optimization. By improving the fields of view, the three dimensional plasma radiation distributions will be reconstructed with higher accuracy.
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