124 
1e 
  
425 
for some applications. The subject image patch is read into the correlator as 
an "A" stream which is "centered" and a "B" stream which is slid by varying 
amounts in x or y. The digital "score" for each image patch displacement is 
stored for further processing. The correlator portion of the processor is in 
an early stage of development and will undergo change as more powerful 
correlator chips become available. With signal processing a grey scale image 
can sometimes be rendered into a binary equivalent, but some information will 
thereby be lost. For images having large dynamic range with intelligence 
imbedded near regions of large contrasting shading, it is anticipated that 
four bit wide correlation of preprocessed images will generally be necessary. 
2.3. Displays and Outputs 
This portion of Fíg. 2 is more conventional, consisting of up to three 
displays and miscellaneous outputs. The latter include an 8 bit digital 
output port to transmit images at any rate, and specialized digital and analog 
control outputs as the application warrants. Displays consist of a monitor 
for the CCD camera to facilitate focussing, centering, etc; of inputs, and an 
output display driven by D/A converters from the frame memory or from the 
processed image output. These are run at various frame rates and resolutions 
on a Tektronix 608 monitor. 
Display specifications depend upon application. For monitoring a process, an 
x, y, Z display run at an arbitrary frame rate will suffice. If measurement 
within the output image is to be pursued, (i.e. video image transfer in 
photogrammetric instruments), a non flickering image is essential. A double 
buffered video display memory (Fig. 2) may be required to minimize visual 
disturbance when the processing rate is slower than the display refresh rate. 
This rate depends upon the display screen persistence. The digital data can 
either be converted to standard TV form of 60 interlaced frames per second on 
black and white phosphor, or displayed at a 20 to 30 percent higher frame rate 
on a low persistence, high resolution monitor (e.g. Tektronix 608). 
A composite correlation window image and analog display of correlation values 
is derived from the digital data and displayed on an oscilloscope as a 
monitor, Fig. 3(b). The 4 bit wide 32K pixel (maximum) windowed image for 
correlation is multiplexed with the output from the correlator 
multiplier/accumulator unit. Each dot in the correlation trace Fig. 3(b) is 
the image matching "score" for the entire M x N pixel window. Dot separation 
in x is a function of image-image displacement and in y is a function of the 
relative correlation or image match value after scaling and D/A conversion. 
The stationary image, Fig. 3(b), which is the "A" input to the correlator, 
Fig. 2, is refreshed at a high frame rate since it is derived from the 
independent high speed correlator memory. The refresh rate of the dot 
sequence in the composite depends upon the total number of frame correlations 
(dots). For 32K pixels at 20MH, they are formed at the rate of one per 1.6 
ms. This display is useful for visualization and observing trends during 
experiments, as illustrated in the results. 
3. Examples of the Experimental Image Processor Capability 
3.1. Image Improvement 
Digital spatial filtering (Hall, 1979, sec. 4.4), is imminently suited to the 
task of rapidly altering the photometric character of an image in any desired 
way. In video transfer systems with the eye as the final transducer, its most 
common use is to remap grey scale so that detail conveyed on a wide range of 
background shading is rendered visible on video display units of reduced