Itseez/opencv — pull request #511 by aritzlc (2013-02-20 15:31:40+00:00)
Title: Thin prism distortion coefficients added to the calibration model. 

Dear Sir or Madam,

I added the thin prism distortion coefficients to the calibration model, being the distortion model:
Xd = Xu *(1+K1*r2+K2*r4+K3*r6)/(1+K4*r2+K5*r4+K6*r6) +
(2*P1*Xu*Yu+P2*(r2+2*Xu^2)) +S1*r2+S2*r4;
Yd =Yu *(1+K1*r2+K2*r4+K3*r6)/(1+K4*r2+K5*r4+K6*r6) + (P1*(r2+2*Yu^2)+2*P2*Xu*Yu) +S3*r2+S4*r4;

I put a new flag CV_CALIB_THIN_PRISM_MODEL, to use the thin prism distortion parameters in the minimization, and also the flag CV_CALIB_FIX_S1_S2_S3_S4 to fix them.

I have done it because for my camera the results are improved by using the thin prism coefficients.
Hoping to be interesting for you,
Yours sincerely,
Aritz.