accuracy of *stereoCalibrate()*

edit

Hi , I wanna get some advices here to improve the accuracy of stereocalibrate(). I calibrate my cameras very succesfuly , with rms <0.3 , but when I use the same images to do stereocalibrate, I get a very large rms. my result of my experiment is as follow.

so is there someone can give me some tips to improve my stereo calibration's result.

thx ->..<-

Updata: I run stereoCalibrate() using those parameters,

stereoCalibrate(ObjectPoints, imagePointsFirst, imagePointsSec,
    intrMatFirst, distCoeffsFirst, intrMatSec, distCoffesSec,
    imageSize, R, T, E, F, CV_CALIB_FIX_INTRINSIC,
    TermCriteria(TermCriteria::COUNT + TermCriteria::EPS, 30, 1e-6));

and calibrate each camera like this,

calibrateCamera(ObjectPoints, imagePoints, imageSize, intrMat, distCoeffs,
    rvecs, tvecs);

and those are parts of my images used for calibrating.

update 2:

I grab the images for calibrating the two cameras at the same time. So dose the images used for stereo calibrations.