deblurring ratio is. As general, if we want to get a good de- 
blurring effect,we must choose a smaller ratio of the reference 
beam to the object beam,the modulations of the fringes are very 
low, so the efficiency of the filter is small.' But'in © this new 
System, the inverse filtering function can be got automatically 
with the help of the mask. We only choose the ratio R/Ajaccord- 
ing to the linear recording condition, so we can get higher mo- 
dulation interference fringes.The other methods can not compare 
with this method in efficiency. And it is verified by  experi- 
ments that there are big differences in efficiency if different 
photographic condition is used. So it isveryv important to  op- 
timize the recording and processing conditions. 
3°. The anti-noise property 
The holographic system is damaged by various noise, espe- 
cially the granularity noise due to random aggregations of the 
silver grains in the emulsion. Heistrom developed an expression 
for the optimum filter function, when random zero-mean,additive 
noise is present. As the criterion for best filtering,the prin- 
ciple of the least mean-squares is used in his derivation. The 
optimum fiiter function is 
Po / ® 2 
Qo / D +1/ IH} 2 
where ¢, , 9, are the power spectra of the noise distribution and 
the image respectively. He showed that the smaller the 9,/9, is, 
the stronger the noise is restrained. From part II we can give 
an another form of our filter 
2XfR / Ao 1 
| *(OCf2R7/A/|C,H |? C,-H 
here ^| 9$4/9«9« A4? f£? (R/Ao )? 40.0014 (for à 6328A, f - 600mm, R/As 1/10), 
it is very small. So the filter we have got is optimal with 
respect to the additive noise. 
Another advantage of this system is that the output image 
is composed of N pictures. So the SNR of N-channel filtering 
system is increased by N times than that of a single one. The 
affection of the system noise is decreased greatly. 
t=H" (18) 
  
(19) 
Le = 
V. Experimental 
The linear motion blur image(Fig.2a) simulated in the labo- 
ratory and the blurred remote-sensing image (Fig.2b) were pro- 
cessed by this: system.The over all Gammas of two blurred images 
were controlled to be 2 approximately. So that their amplitude 
transmittances are proportional to the irradiation  distribu- 
tions of the blurred objects. 
The image shown in Fig.2b was the deblurred one of  Fig.2a 
using the 3-channel inverse filtering system. The sharpness of 
the restored picture was improved greatly and most of the de- 
tails blurred was almost restored. 
Fig.2 is the restored remote sensing image. In order to 
evaluate the capacity of the filtering system, we chose a part 
of the resolution test marks from an aero-photograph. From the 
ratio of ground speed to the flight height (V/H) of the  aero- 
plane as well as other references the blur width was figured 
out, which was 100um. If we observe this photo directly, the 
42