NCJ Number
13383
Date Published
1973
Length
34 pages
Annotation
DISCUSSION OF PARAMETERS OF NIGHT VISION DEVICES THAT AFFECT IMAGE QUALITY.
Abstract
IMAGE QUALITY IS PROBABLY THE SINGLE MOST IMPORTANT FACTOR IN DETERMINING THE UTILITY OF ANY OPTICAL DEVICE. FOR NIGHT VISION DEVICES, IN PARTICULAR, IT IS OF PARAMOUNT IMPORTANCE. IN LOOKING AT TWO DIFFERENT PHOTOGRAPHS OF THE SAME SCENE, WHICH ARE ESSENTIALLY TWO DIFFERENT IMAGES FIXED BY THE PHOTOGRAPHIC PROCESS, ALMOST ANYONE CAN TELL AT A GLANCE WHICH HAS THE BETTER IMAGE QUALITY. OBJECTIVE EVALUATION OF IMAGE QUALITY IN QUANTITATIVE TERMS, HOWEVER, IS NOT EASY, BECAUSE THERE ARE MANY VARIABLES INVOLVED, NOT ALL OF WHICH HAVE BEEN IDENTIFIED, OR CAN BE QUANTITATIVELY EVALUATED. AT LEAST FIVE PARAMETERS ARE REQUIRED TO DESCRIBE THE IMAGE QUALITY OF A NIGHT VISION DEVICE - (1) CONTRACT TRANSFER FUNCTION (CTF), (2) DISTORTION, (3) LIGHT INDUCED BACKGROUND, (4) LIGHT EQUIVALENT BACKGROUND, AND, (5) FLARE. THE TESTS REQUIRED TO EVALUATE THE IMAGE QUALITY OF THE NIGHT VISION DEVICE SHOULD INCLUDE (1) CTF MEASUREMENTS AT SPATIAL FREQUENCIES FROM NEAR ZERO TO THE FREQUENCY AT WHICH THE CTF APPROACHES ZERO, (2) DISTORTION MEASUREMENTS, (3) LIGHT INDUCED BACKGROUND MEASUREMENTS, AND (4) A QUALITATIVE EVALUATION OF FLARE. THIS REPORT IS A PRELIMINARY SURVEY OF IMAGE QUALITY EVALUATION TECHNIQUES LEADING TOWARD A STANDARD FOR NIGHT VISION DEVICES. APPENDED MATERIAL CONTAINS DETAILED EXPLANATIONS OF THE TECHNICAL NOMENCLATURE USED THROUGHOUT THE DISCUSSION. (AUTHOR ABSTRACT MODIFIED) (SNI ABSTRACT)