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Showing papers on "Aerial image published in 1972"


Journal ArticleDOI
TL;DR: The modulation transfer function of the dioptrics of fifteen cat eyes was determined and each MTF was used to calculate the light distribution within the retinal image of stimuli of various geometry used in experiments on retinal ganglion cells in the same eye.
Abstract: 1. The modulation transfer function (MTF) of the dioptrics of fifteen cat eyes was determined. The aerial image, formed by the eye of a standard object (a 0.5-1.0 degrees annulus), was photographed. The transmission of the film negative was measured with a scanning microdensitometer to yield the light distribution within the aerial image. Correcting for the double passage, this experimentally determined light distribution and the known object light distribution were used to obtain the MTF, applying Fourier methods. Each MTF was used to calculate the light distribution within the retinal image of stimuli of various geometry used in experiments on retinal ganglion cells in the same eye.2. When the eye was equipped with an artificial pupil of the same size as that used in the neurophysiological experiments (4.0-4.8 mm diam.) the MTF had fallen to 0.5 at 2.43 c/deg. When the pupil was removed the MTF had fallen to 0.5 at a much lower spatial frequency (1.0 c/deg). This shows that even when one uses an artificial pupil too large to provide optimal image quality there is a vast improvement over using no pupil.3. These image quality measurements were prompted by the need to know the actual stimulus image in experiments on the functional organization of the receptive field, a need exemplified in this paper by a few specific physiological results. The full neurophysiological results appear in the next two papers.

23 citations


Journal ArticleDOI
TL;DR: In this paper, the focus for a single well-chosen frequency can be a good index for all frequencies in the photographically important region of the MTF of the lens, also that a through-focus plot of modulation at one or two important frequencies is often of greater value to the camera manufacturer than the usual MTF plot at one focus position.
Abstract: Photoelectric measurement of aerial image modulation at a single spatial frequency has been applied to the focusing of lenses in aerial cameras. Using an automated apparatus to provide a plot of modulation through focus, the settings are made in a fraction of the time and with much greater confidence than by the photographic resolving power method. It is pointed out that the focus for a single well-chosen frequency can be a good index of the focus for all frequencies in the photographically-important region of the MTF of the lens, also that a through-focus plot of modulation at one or two important frequencies is often of greater value to the camera manufacturer than the usual MTF plot at one focus position. The well-known difficulty in focusing some lenses by high contrast resolving power is explained in terms of their decreased sensitivity to focus setting above a certain frequency; in some cases this effect cannot be eliminated by moderate stopping down. Although primarily designed for measuring relative modulation on axis, the apparatus can be calibrated to read absolute modulation to a useful degree of accuracy, can be used off-axis, and has many photo-optical applications.

1 citations


Journal ArticleDOI
TL;DR: In this paper, a method for increasing the linear dynamic range of coherent-optical spatial filters, with special reference to holographic image-deblurring filters, is presented. But the results show that a good transfer function can be achieved with a hologram-only filter.
Abstract: We report on a new method for increasing the linear dynamic range of coherent-optical spatial filters, with special reference to holographic image-deblurring filters. In the filter-generating step, a transmission grating is placed in contact with the transparency representing the spread function of the blur. The spectrum of the spread function then appears in a series of equally spaced islands of different intensities, each occupying a different region of the nonlinear characteristic of the recording medium. Each spatial frequency can then be properly exposed somewhere on the filter, even with a film of limited dynamic range. In the image -processing step, the grating is superposed on the blurred image, the spectrum of which then falls on all the islands of the filter. In this way, the filtering operation is done in parallel channels, each with a different nonlinear characteristic. The channels are combined in the output plane by superposing a grating on the filtered aerial image and viewing this plane through an optical system that does not resolve the grating. Theory, computer simulations, and experimental results are presented. The results show in particular that a good transfer function can be achieved with a hologram-only filter.

1 citations