PHYSICS SECTION '62 
for 2 u ' < 0. 8 rad (¡=45°). . . . . . mm 
used with spectacles mm 
Low Mi 
High M2 
Ratio M2/M1 
1 of 23 x 23 Cm2 print) at Mi 
at M2 
Concentricity of areas (in % r 2) 
"Optical axis" angle with perpendicular on print mrad 
Eye-base + range of adjustment mm 
Separation between corresponding points on prints cm 
Parallax adjustment for height differences Ax cm 
Differences in Magnification between right and left (% or A y) mm 
Model-curvature by Distortion (subjective) 
Rotation of one image to the other (milli-radians) 
Re-orientation when changing M2 -» Mi: A y mm 
: rotation mrad 
Observed area of stereo-model (in % of A (point 4)) 
Scanning and Double Scanning 
Scanning : parallel shifting of 
Parallax adjustment: Ay (mm) (Ax is less critically) 
•Y-parallax introduced by non-parallel scanning .... 
Total area which can be scanned 
"Optical axis" angle with _L on print when scanning . . 
Image Recording 
Size of exit pupil diameter 
Transmitivity of stereoscope for white light 
Illumination at retina in % of unaided vision 
Flare as % of average brightness (luminance) of 23 x 23 
(measured on area with Q = 1/M cm) of 10 cpn^ 
Illumination under practical conditions (subjective) . . 
False images (subjective) . . 
Direct Flare into the eye (subjective) . . 
. mm 
. cm 
. mrad 
Image Quality 
Transfer Function approx, by a Gauss-TF : -* 2 cr of SF . . . pm 
Spatial frequency at 50% contrast lines/mm 
Difference in Image Quality between x and y direction 
Central area of good Image Quality (% of A (point 4)) 
Useful focussing range of eyepiece dioptre 
Refocussing needed when changing Magnification M2 -* Mj. dioptre 
Good 
Tolerable 
Poor 
> 0. 9 
0. 7-0.9 
< 0.7 
> 15 
12-15 
8-12 
> 25 
20-25 
0. 8-1.0 
1.0-1. 5 
0. 6-0. 8 
3-4 
4-6 
> 6 
2-3 
3-4 
4-6 
> 60% 
30-60% 
< 30% 
> 10% 
2-10% 
< 2% 
< 20% 
< 20 
20-40 
> 40 
65+10 
64+8 
64+5 
> 25 
21-25 
< 21 
-1 - +3 
+1 
< 1%;1/M 
1-3% 
> 3%;3/M 
< 10 
10-20 
> 20 
< 1/M 
1/M-3/M 
> 3/M 
< 10 
10-20 
> 20 
> 90 
80-90 
prints 
opt. axes 
scope 
> +10 
< 1/M 
1/M-3/M 
> 3/M 
20x23 
< 20 
20-200 
3-4 
4-5 
2-3 
> 50% 
40-50% 
25-40% 
> 50% 
25-50% 
10-25% 
< 3% 
3-10% 
10-20% 
< 2%? 
2-5% ? 
5-10% 
easy 
moderate 
hard 
no 
at edge 
at centre 
no 
some 
more 
< 15 
15-25 
> 25 
> 35 
20-35 
< 20 
no 
10% 
10-20% 
> 90% 
50-90% 
< 50% 
- +6 
+ 5 
one < 5 
< +0. 5 
0. 5-1 
> ±1 
100 
100% Modulation 
- 
Modulation 
Transfer 
- 
Ft 
incti 
DÌÌ Oil 
xis 
- 
- 
1 
0 1/mm 
15 20 30 40 
Observed Area at Magn. 
Area of constant quality