The Calculation of Image Quality

The Effective Instantaneous Field of View (EIFOV) is a new specification for defining system performance that takes into account the system MTF and provides a convenient way to specify and compare the performance of imaging and radiometric systems. The use of EIFOV is illustrated by two examples of first-order designs, each using ƒ/3·5 optics having a diffraction-limited MTF over the spatial frequency range of interest. The systems are to detect reflectance differences of 0·01 with an EIFOV of 30 m in a wavelength interval of 600 to 700 nm from an altitude of 1000 km. One system uses a solid-state array having a noise equivalent signal of 1·0 μJ/m2 and elements 15 by 15 μm in size; the other uses aerial film with a diffuse RMS granularity of 0·008. These examples serve to point out the basic differences between electro-optical and photographic systems for imaging through the atmosphere. Assuming they are of the same size, an electro-optical system is preferred when radio-metric measurements of the imagery...

Use of MTF in the Specification and First-order Design of Electro-optical and Photographic Imaging and Radiometric Systems

Intensity distribution in the diffraction images of truncated one-dimensional periodic objects formed in the presence of linear image motion by a diffraction-limited optical system has been studied. Incoherent sine and square wave objects have been considered with a various number of cycles and for various degrees of image motion. The graphical presentation of results clearly shows the degradation in the image due to linear motion blur. Image contrast and average irradiance have been tabulated for a number of cases. For certain values of the motion parameter spurious resolution results. It has been found that the number of periods in the target required to approximate a target with infinite number of periods in the presence of linear motion is more than that in the absence of motion. For certain values of linear motion blur, the contrast remains zero irrespective of the number of periods considered.

Diffraction images of truncated sine and square wave periodic objects in the presence of linear image motion.

EXPERIMENTS WITH LABORATORY AND AERIAL PHOTOGRAPHS IN COMBINATION WITH THEORETICAL CONSIDERATIONS HAVE COMPARED THE IMAGING CHARACTERISTICS OF PHOTOGRAMMETRIC CAMERA SYSTEMS WITH THOSE OF RECONNAISSANCE, MULTISPECTRAL, AND RETURN-BEAM-VIDICON SYSTEMS CONSIDERED FOR AEROSPACE USE. FROM THESE EXPERIMENTS IT IS ESTIMATED THAT PHOTOGRAMMETRIC CAMERAS IN COMBINATION WITH HIGH-QUALITY RECONNAISSANCE FILMS WILL PROVIDE HIGH-ALTITUDE AERIAL PHOTOGRAPHY WITH IMAGE QUALITIES COMPARABLE TO THOSE OBTAINED WITH RECONNAISSANCE AND MULTISPECTRAL SYSTEMS. IT ALSO SEEMS POSSIBLE TO USE CURRENTLY AVAILABLE PHOTOGRAMMETRIC CAMERA SYSTEMS IN PLACE OF RECONNAISSANCE SYSTEMS TO OBTAIN SPACE PHOTOGRAPHS OF GOOD QUALITY AT ABOUT 1:380,000 SCALE. THESE PHOTOGRAPHS WOULD BE SUITABLE FOR THE COMPILATION OF PLANIMETRIC MAPS TO 1:24,000 SCALE IF ADEQUATE VIEWING MAGNIFICATION IS AVAILABLE IN THE PLOTTING INSTRUMENT. FURTHERMORE, SUCH PHOTOGRAPHS COULD ALSO BE USED TO ESTABLISH SUPPLEMENTAL CONTROL, TO PRODUCE PHOTOMAPS AND TO MAKE REASONABLY DETAILED STUDIES OF EARTH RESOURCES. THE ECONOMIC BENEFITS OF USING SMALLER-SCALE IMAGERY FOR MAPPING TASKS INCLUDE THE REPLACEMENT OF SEVERAL OLDER PLOTTING MACHINES BY ONE PRECISION MECHANICAL-PROJECTION OR ANALYTICAL INSTRUMENT OF GREATER VERSATILITY AND ACCURACY. DETAILED EARTH RESOURCES STUDIES ARE FEASIBLE WITH IMPROVED HIGH-ALTITUDE AERIAL PHOTOGRAPHS, PARTICULARLY IF BETTER COLOR-INFRARED FILMS CAN BE MANUFACTURED. THE SMALL-SCALE SPACE-IMAGERY TO BE PRODUCED BY THE ERTS-A SYSTEM WILL BE USEFUL FOR VERY GENERALIZED REGIONAL STUDIES OF EARTH RESOURCES. SKYLAB EXPERIMENTS ARE PLANNED TO PROVIDE MULTISPECTRAL AND HIGH-RESOLUTION PHOTOGRAPHS USEFUL FOR BOTH RESOURCE STUDIES AND PHOTOMAPPING; HOWEVER, THE INCLUSION OF A METRIC CAMERA IN SKYLAB WOULD GREATLY ENHANCE ITS VALUE TO THE CARTOGRAPHER. /AUTHOR/

Quality and applications of aerospace imagery

Les techniques de la transformation Fourier dans le cadre de la theorie de diffraction scalaire sont utilisees pour calculer les images par diffraction des objets tronques, periodiques dans une dimension. Nous avons traite des objets incoherents avec des profils d'onde triangulaires et les effets des images floues (blur) a cause d'un mouvement lineaire d'objet. Les spectres de frequence dans l'espace de l'objet ont ete calcules. et traces. Nous presentons sous forme de tableau le contraste d'image et l'eclairement moyen pour plusieurs cas. Les resultats sur la distribution d'eclairement des images sont donnes sous forme graphique afin de permettre des estimations rapides de performance, ils representent une aide precieuse pour l'analyste des images. Les formules sont donnees pour un systeme optique quelconque, mais les resultats sont limites au cas d'ouverture circulaire du systeme.

https://iopscience.iop.org/article/10.1088/0029-4780/3/6/303/pdf

Images of truncated triangular-wave periodic targets in optical systems in the presence of linear image-motion

This paper describes studies of the threshold modulation curve for photographic film. The threshold modulation curve is an empirically derived relation showing the need at any spatial frequency for modulation in the aerial image of a tribar for resolution to be achieved. The paper deals with the history, raison d'etre, theory, method of measurement, and accuracy and precision of the threshold modulation curve. The statistical aspects of the threshold modulation curve are emphasized, and the influence of factors that cause variations in the curve are examined. Examples are given of current and potential applications of the threshold modulation curve.

T. F. Kerwick

Papers

Threshold Modulation Curves for Photographic Films