Target identification performance as a function of low spatial frequency image content

2000 ◽  
Vol 39 (9) ◽  
pp. 2458 ◽  
Author(s):  
Ronald G. Driggers
Keyword(s):  
Spatial Frequency ◽  
Target Identification ◽  
Identification Performance ◽  
Image Content

Impact of speckle on laser range-gated shortwave infrared imaging system target identification performance

2002 ◽  
Author(s):  
Ronald G. Driggers ◽  
Richard H. Vollmerhausen ◽  
Nicole M. Devitt ◽  
Carl E. Halford ◽  
Kenneth J. Barnard
Keyword(s):  
Infrared Imaging ◽  
Imaging System ◽  
Target Identification ◽  
Identification Performance ◽  
Laser Range ◽  
Infrared Imaging System ◽  
Shortwave Infrared

scholarly journals QUANTIFYING DEPTH OF FIELD AND SHARPNESS FOR IMAGE-BASED 3D RECONSTRUCTION OF HERITAGE OBJECTS

2020 ◽  
Vol XLIII-B2-2020 ◽  
pp. 911-918
Author(s):  
E. K. Webb ◽  
S. Robson ◽  
R. Evans
Keyword(s):  
Spatial Frequency ◽  
3D Reconstruction ◽  
Frequency Analysis ◽  
Input Image ◽  
Depth Of Field ◽  
Image Sharpness ◽  
Image Content ◽  
Model Quality ◽  
Output Quality ◽  
Spatial Frequency Analysis

Abstract. Image-based 3D reconstruction processing tools assume sharp focus across the entire object being imaged, but depth of field (DOF) can be a limitation when imaging small to medium sized objects resulting in variation in image sharpness with range from the camera. While DOF is well understood in the context of photographic imaging and it is considered with the acquisition for image-based 3D reconstruction, an “acceptable” level of sharpness and associated “circle of confusion” has not yet been quantified for the 3D case. The work described in this paper contributes to the understanding and quantification of acceptable sharpness by providing evidence of the influence of DOF on the 3D reconstruction of small to medium sized museum objects. Spatial frequency analysis using established collections photography imaging guidelines and targets is used to connect input image quality with 3D reconstruction output quality. Combining quantitative spatial frequency analysis with metrics from a series of comparative 3D reconstructions provides insights into the connection between DOF and output model quality. Lab-based quantification of DOF is used to investigate the influence of sharpness on the output 3D reconstruction to better understand the effects of lens aperture, camera to object surface angle, and taking distance. The outcome provides evidence of the role of DOF in image-based 3D reconstruction and it is briefly presented how masks derived from image content and depth maps can be used to remove unsharp image content and optimise structure from motion (SfM) and multiview stereo (MVS) workflows.

Effectiveness of Filters in Improving Air-to-Ground Target Identification Performance on a Television Display

1968 ◽  
Vol 10 (5) ◽  
pp. 489-492 ◽  
Author(s):  
Dorothy M. Johnston
Keyword(s):  
Analysis Of Variance ◽  
Target Identification ◽  
Video Tape ◽  
Identification Performance ◽  
Television Camera ◽  
Reliable Difference ◽  
Ground Target

The purpose of this study was to determine if the utilization of filters would improve target identification performance on a television display. Inflight video tape was obtained of convoys of vehicular targets under different meteorological visibility conditions while using two types of filters and a no-filter condition on the television camera. The video tape was used in the laboratory for dynamic presentations on a television display. Analysis of variance revealed with five miles visibility no reliable difference in target identification slant ranges between filters 15 and 29, but reliable differences between filter 15 and no filter, and between filter 29 and no filter. With seven miles meteorological visibility reliable differences in target identification performance were found between all combinations of the conditions investigated. Maximum mean improvements in performance were as follows: with five miles visibility filter 15 increased target identification range 2600 feet farther than the no-filter condition. With seven miles visibility filter 29 increased target identification range 3685 feet feet farther than the no-filter condition.

scholarly journals Effects of Spatial Frequency Filtering Choices on the Perception of Filtered Images

Vision ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 29
Author(s):  
Sabrina Perfetto ◽  
John Wilder ◽  
Dirk B. Walther
Keyword(s):  
Spatial Frequency ◽  
Behavioral Outcomes ◽  
High Spatial Frequency ◽  
Frequency Content ◽  
Frequency Filtering ◽  
Image Content ◽  
Specific Choice ◽  
Spatial Frequencies ◽  
Spatial Frequency Filtering ◽  
Frequency Components

The early visual system is composed of spatial frequency-tuned channels that break an image into its individual frequency components. Therefore, researchers commonly filter images for spatial frequencies to arrive at conclusions about the differential importance of high versus and low spatial frequency image content. Here, we show how simple decisions about the filtering of the images, and how they are displayed on the screen, can result in drastically different behavioral outcomes. We show that jointly normalizing the contrast of the stimuli is critical in order to draw accurate conclusions about the influence of the different spatial frequencies, as images of the real world naturally have higher contrast energy at low than high spatial frequencies. Furthermore, the specific choice of filter shape can result in contradictory results about whether high or low spatial frequencies are more useful for understanding image content. Finally, we show that the manner in which the high spatial frequency content is displayed on the screen influences how recognizable an image is. Previous findings that make claims about the visual system’s use of certain spatial frequency bands should be revisited, especially if their methods sections do not make clear what filtering choices were made.

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