Establishment of the Fourier transform image analysis and the three-dimensional development to the tropical wood species.

为了利用傅里叶变换图像分析技术(FTIA)对木材细胞结构进行定量评价，研究了木材细胞结构的一般方法及其背景。FTIA由三个主要步骤构成，即图像域上的前FFT步骤、二维FFT步骤和频域上的后FFT步骤。提出了FFT前提取结构元素和形状因子的映射步骤。验证了后FFT中的一些新问题，如频率范围、频率误差、方向问题等。特别是详细分析了图像域对比度与频域功率级之间的关系，并提出了一些仿真方法来评估误差程度和克服误差。发现了快速傅立叶变换的一种特殊性质，即把一个象素或一个象素宽度的直线识别为δ函数，这一特性对于卷积技术的应用是有效的，这有助于控制功率水平。然而，历史悠久但很少在实际应用中应用的三维分析的体视学对一些热带木材，如马占相思，提出了挑战

For the quantitative evaluation of wood cell structures using Fourier transform image analysis(FTIA), which has been developed by the authous, general procedures and their backgrounds were examined. The FTIA was constructed by three main procedures, namely, pre-FFT step on the image domain, two dimensional FFT and post-FFT step on the frequency domain. Mapping procedures in the pre-FFT extracting structural elements and shape factors are proposed. Some new problems in the post-FFT such as frequency scale, frequency errors, direction problem and so on were verified. Especially, relations between contrast on the image domain and power level on the frequency domain were inspected in detail, and then some simulations were proposed to evaluate the degree of errors and to overcome them. A peculiar nature of FFT that one pixel or line of one pixel width is recognized as the δfunction was found out, and the peculiarity is shown to be effective for the application of the convolution techniques which is useful to control power level.Succeedingly, the stereology for the three dimensional analysis, which have long history but has been rarely applied in practical view, is challenged to some tropical timbers such as Acacia mangium