Blank Frames Research Articles

Rapid iconic erasure without masking

We report on the erasure of the iconic memory of an array of 12 black letters flashed on a continuously- present white field. Erasure is accomplished by replacing the 16 ms letter array (frame 1) with a blank white frame for 16 ms (frame 2). The letter array returns in frame 3, with from one to six letters missing. Report of the missing letters is accurate without the blank white frame but is impoverished with it, as if interposing the blank erases the icon. Erasure occurs without any obvious luminance masking, 'mud splashes', pattern masking (backward, forward, or metacontrast), lateral masking, or masking by object substitution. Erasure is greatly decreased if the blank is presented one frame earlier or later. We speculate that erasure is due to a rapid reset of the icon produced by an informational mis-match.

Digital autoradiography imaging using direct irradiation of a CCD between 278-309 K

Using direct irradiation of a CCD for beta autoradiography is principally limited by variations in cumulative pixel dark current across the device modulated by small changes in temperature. We have used a modified fixed pattern noise correction method to address this problem at room temperature, and tested the method using /sup 14/C microscales and labeled mouse tissue samples. An evaluation is included of the minimum activity levels which can be detected between 278-309 K, determining the quantitative and qualitative imaging capabilities and improvements of such an approach for imaging distributed sources (such as the microscales) at various levels of activity. Further investigation is presented of the effects of large temperature changes between acquisition of real data and blank frames used for image correction. Empirical formulas describing the relative dark current thermal behavior have been developed and applied to low activity, distributed sources such as /sup 14/C microscales and thin tissue mouse brain sections labeled with /sup 35/S. The corrected images obtained by the CCD-based imaging system were compared with digitized film images of the same samples. It was found that the proposed approach can successfully detect weak distributions from radiolabeled tissue at room temperature.

A microcomputer based digital imaging system for ion microanalysis

SUMMARYA microcomputer based digital imaging system was developed for a Cameca IMS‐3f ion microscope permitting real‐time digital acquisition of secondary ion images. Image signal‐to‐noise enhancement results from random noise reduction by real‐time ensemble averaging and from a reduction of pattern noise in the charge injection device (CID) array by subtraction of blank frames. Acquired images comprise 244times248 pixel arrays with 8‐bit intensity resolution. Images are displayed on a colour monitor in a grey scale or pseudo‐colour using one of four programmable lookup tables. Image processing software permits off‐line ion image enhancement and manipulation as well as multitechnique digital image correlations. System capability is illustrated by a biological example involving digital imaging studies of Al distribution in osteomalacic bone tissue, including correlative light microscopy and ion microanalysis.