Optical filtering techniques in digital image enhancement.

Image processing by linear systems has some fascinating aspects due to the theorems of the Fourier transform (FT). Those, whose FT operator is a piece of glass are quite familiar to them, thinking in object space images and FT space images by reason of visual experience. But also in digital image processing the study of FT images is advantageous, e. g. when designing linear filters. The first step of the realization of a Laplacian operator is shown as an example

Enhancement of cell and chromosome images using optimized filter masks in Fourier transformed space.

Image processing by linear systems has some fascinating aspects due to the theorems of the Fourier transform (FT). Those, whose FT operator is a piece of glass are quite familiar to them, thinking in object space images and FT space images by reason of visual experience. But also in digital image processing the study of FT images is advantageous, e.g. when designing linear filters. The realization of an apodized Laplacian operator is shown, using an image of G-banded chromosomes as test objects. The quality of the filters is tested by the application of a contour-algorithm onto the filtered images

Spectral blue-shift of red edge minitors damage class of beech trees.

Beech trees were classified by ground-based inspection using the German Tree Damage Classification Scheme. Reflectance of a number of leaves from each tree was measured with high spectral resolution, and the wavelength of the maximum inflection point (MIP) of the red edge was determined. Statistical analysis shows that there is a monotonous blue-shift of the MIP with damage class, as well as monotonous decrease of the difference of the MIP obtained from adaxial and abaxial measurement on leaves

Detection of abnormal cells by optical image processing.

Optimized image formation is an essential step preceding automatic image analysis. We report about an optical device for automatic prescreening of cervical cytologic samples. The system should detect abnormal cells. Using band-pass filtering in the Fourier plane a detection of abnormal cells is possible. The main advantage of this method is its ability of parallel processing in real time. That means we can handle a large object field at once in a microscope. We use a very simple parameter -the size of the cell nucleus- for a discrimination between normal and abnormal cells. As a typical result the detection of abnormal cells in a Papanicolaou smear by band-pass filtering is showed

Extension of the spatial frequency range of Fourier holograms by double exposure.

In Fourier holography the transfer of the total diffraction limited spectrum normally is prevented by the limited dynamic range of the photographic plate. We show that a broader frequency band can be transferred if registration is done consecutively at a respectively adjusted bias. The principle is explained by means of a simple model. © 1971

Reflectance and Fluorescence Parameters of Needles of Norway Spruce Affected by Forest Decline.

The reflectance spectrum R(λ) in the range between 366 nm und 780 nm and the fluorescence induction kinetics with a maximum time resolution of 10 μs have been determined from needles of spruce trees with the damage classes S0/S1, S2, and S3. The reflectance values R660 and R710 at 660 nm and 70 nm, respectively, the infraredred ratio R760/R660, the position λre of the inflection point of R(λ) at the red edge, the chromaticity point, and the initial and steady-state ratio of the fluorescence intensities at 685 nm and 730 nm are shown to indicate the degree of damage. A quantitative comparison between the data obtained from the reflectance spectrum and the fluorescence measurements demonstrate that both methods provide a similar capability to distinguish between the trees of different damage classes