Jaksic, 
corder, 
onsumer 
anufac- 
based, 
ordable 
lis ran 
antity. 
th the 
'S were 
every 
The 
ion of 
ietric) 
on and 
ues on 
louke, 
image 
frames 
82. 
range 
id low 
noise 
n the 
set by 
achine 
Leving 
poling 
duced 
ittern 
r CCD 
mper- 
sink. 
ed by 
with 
ed in 
large 
TE of 
ignal 
9 has 
Unlike fine grained photographic emulsions, solid state imagers have a 
well defined geometry of the active illumination regions, imposed by the 
particular technology employed. Photosites are isolated rectangular or 
square regions typically 12 um to 55 um on a side. Some portions of the 
array will be masked so as not to be photon active. This varies from 
approximately 10% for the frame transfer device, which has nearly contiguous 
pixels in each direction, to more than 50% for some interline CCD devices, 
Real, 1986. This loss of spatial sampling may be intolerable for some 
applications in photogrammetry, favoring therefore the use of frame transfer 
CCD's. 
Large format is especially interesting for the photogrammetrist for its 
electronic photography potential, where electronic imagery conveys useful 
pieces of photographic data bases to the user. By contrast, for some 
industrial flow applications, even 300 TV frames per second may be 
insufficient, requiring small ‘format, high bandwidth cameras or special 
custom designs for high speed, Lee, 1982. A commercial grade 1000x1000 
pixel imager is still two years away, Cohen, 1986, emerging from the massive 
effort on HDTV. The existence of high density CCD's simulating the image 
producing quality of the highest grade 24 inch camera has been forecast, 
Ravich, 1986. Electronic still photography of 35 mm grade images is 
predicted in five years time. Texas Instruments pioneered the large format 
CCD with its 800x800 pixel device for space exploration, (i.e. Voyager II 
mission), Norris, 1981, followed by a 1024x1024 pixel imager. The impact 
upon applications requiring real-time processing is that the data throughput 
of such large imagers can easily exceed the bandwidth of existing digital 
image processors. 
All solid state imagers have some blemishes, an admission they are not 
100% perfect. This was a serious consideration with early devices where 
some photo elements had lower sensitivity than the average plus a high dark 
current. Yields of high quality devices are much better now and, with cool- 
ing, "defective" pixels marring an image will cease to be an issue except 
for low light level applications, where a premium device must be bought and 
cooled. 
Spectral bandwidth has increased to the point where it is possible to 
consider building two dimensional spectrometers covering the range from 1 A 
to. 11. 000. A, Blouke, .1985. This very advantage, plus the particular 
geometry of solid state imagers, places a greater burden on optical designs 
for solid state cameras. An advanced solid-state array spectroradiometer 
has been fabricated with 32 channels covering 400 to 850 nm, Stewart, 1985. 
It is capable of radiometric measurements in all of its 32 bands with 
variable frame rate and 12 bit output. 
Blooming has been an ongoing problem in solid-state sensors (lowest in 
the CID imager, Real, 1986) due to the existence of stray paths for carriers 
when there is excess illumination. It is manifested by bright highlights 
exceeding their true dimensions and, depending upon imager design, column 
dropouts in the image. Fortunately, badly needed advance is occurring so 
that this factor may be diminished to a negligible level. 
Until recently large area imagers did not have the charge transfer 
bandwidth necessary to sustain a video rate of 30 frames per second. This 
parameter is being met in emerging devices for high definition television 
(HDTV) systems, which, it is anticipated, will result in affordable large 
area imagers by 1988. 
87