Yuri Knizhnikov 
  
The quantitative value of L, characterizes quality of discrete stereomodel formed in visual centers of a brain. 
It is known that the representational properties of images are traditionally estimated on special photographic test- 
objects. In practice of researches the different kinds of photographic test-objects are applied (Frieser, 1975), thus all 
their known types are intended for an estimation of single image quality. The estimation of plastic of stereomodels 
demands producing and usage of spatial test-objects. Certainly, it is desirable, that the form of spatial test-objects is 
corresponded to the forms of a relief of a surface or other three-dimensional objects of terrain, and their texture - figure 
of the landscape features on images. 
The stereo test-objects consisting of triplet of stereoscopically conjugated images were designed and produced for an 
estimation of quality of discrete stereomodels and its changes which characterized by value of a threshold of perception 
of spatial depth and the size of a pixel of discrete images of a stereo pair. At construction of stereo test-objects the 
results of researches (Knizhnikov, 1967) were allowed, and the formation of triplets is implemented according to a 
method (Knizhnikov, 1997), ensuring simultaneous observation by the person of two stereomodels - reference and 
investigated. As a result of developments six elementary stereo test-objects (figures 5a-5f) as gnomonic projection of a 
truncated cone obtained from two points of view - of the left-hand and right-hand eye were produced thus the right-hand 
discrete picture is formed by pixels of the different sizes (accordingly, 0,3; 0,6; 0,9; 1,2; 1,5; 1,8 mm). 
The experiments on stereo test-objects with elementary form and texture have confirmed that the offered method is 
suitable for an estimation of influencing of the size of a pixel on quality of stereomodel. The comparative estimation of 
the left-hand (analogue) and right-hand (discrete) test stereomodels demonstrates that increase of the size of pixel 
results in a decrease of quality of an accepted stereoscopic effect. This process is accompanied also by geometrical 
transformations of discrete stereomodel - in our case by its flattening. The detected feature can be quantitatively 
characterized by the introducing of a flattening coefficient of stereomodel which one is equal g; (0< g;<1), i.e. 
AL AL 
sos oO. 19 
8L AL, pix (19) 
ALand AL, - values of a threshold of stereoscopic perception of spatial depth of stereomodels formed on analogue and 
discrete images, accordingly. 
With allowance for formula (19) formula (17) will be converted as: 
AL, 
ge 
  
I 
b 
For a stereo pair of discrete images produced by pixels of the square form with defined size (pixc), the coefficient of 
flattening (gr) can be calculated as g; 2 0,7 - AL; /pix, in relation to analogue stereomodel with the AL;-resolution. 
Formula (20) was used for estimation of properties of stereomodel observed on discrete aerospace images. It is known, 
that the value of a threshold of perception of spatial depth of a stereo pair of images with allowance for of factor of 
increase of an observation system (v), altitude (L) and basis (B) of surveying is calculated under the formula (Sciridov, 
1959): 
I 
AL=—.- 
Bv 
Vi. (21) 
At observation of images with increase (v) linear value of a sharpness of stereovision is calculated as AL, = Lv,/v, so 
with allowance for of formulas (15)- (18) formula (21) for stereo pairs of discrete images can be shown, as 
AL, = == . (pir? + pit), (22) 
B 
or (with allowance for of formula 20) 
  
510 International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000.