I have extracted Rotation and Translation matrices from the essential matrix. The translation vector has a scale ambiguity. Therefore, I couldn't define its "true" values.
My steps were as follow:
F=estimateF(matches1,matches2,'RANSAC')
E=K2'*F*K1
[U S V]=svd(E)
s=(S(1,1)+S(2,2))/2
S=diag([s s 0])
E_new=U*S*V'
[U S V]=svd(E_new);
R1=U*W*V'
R2=U*W'*V';
t1=U(:,3);
t2=-t1
My problem is how to define the translation of the second camera from the first one in mm.