camera calibration for measuring objects

Hi. in the help of matlab for Measuring Planar Objects with a Calibrated Camera, a checkboared is used . this checkboard is beside the penny for measuring the diameter of it. i want to know that is there any way to measure diameter of penny without the checkboard , I mean that first use the checkboard for calibrating and then use penny in the another picture and measure it's diameter separately.

Answer 1

[Dima Lisin]

To measure a planar object with a single camera you need to know the extrinsics, which is the transformation between the plane of the object and the camera's coordinate system. You can take a picture of the checkerboard on the table separately and compute the extrinsics. You can then take a picture of the penny on the same table and measure it, but the camera must not move between these two pictures.

Alternatively, you can calibrate a stereo pair of cameras using the Stereo Camera Calibrator app, and then you would not need the checkerboard at all. You would also be able to measure non-planar objects.

Answer 2

[Walter Roberson]

Yes. Even if you do not use the Computer Vision routines for Camera Calibration, you can use the checkerboard to compute the projection information, and then on the next picture you use the same calculated projection information to find the size of the object.

[forough j]

thanks for your answer.im new in matlab.i want to calculate the diameter of an object in millimeter. the code which is in the help of matlab can be used when the object(which want to calculate it's diameter) is beside the checkboard.could you please tell me which part of this code (in the help of matlab) I must change to calculate the object separatly? or if you have another code which can help me . thanks