Method of calibrating a camera

1. A method of performing an absolute length calibration for an object ( 20 ) located with or covered by a camera device ( 15 ) in a mirror ( 10 ), the method comprising the steps of:

determining a length of the camera device ( 15 ) based on the type of the camera device ( 15 ),

capturing an image, using the camera device ( 15 ), of the camera device ( 15 ) and the object ( 20 ),

measuring a length of the image of the object ( 20 ) and measuring the length of the image of the camera device ( 15 ) from the captured image,

deriving a calibration function from the determined length of the camera device ( 15 ) and the measured length of the image of the camera device ( 15 ), and

using the measured length of the image of the object ( 20 ) and the calibration function to calibrate the length of the object ( 20 ).

2. The method according to claim 1 , the length of the camera device ( 15 ) comprises lens diameter of the camera device ( 15 ), lens to edge length of the camera device ( 15 ), width of the camera device ( 15 ), height of the camera device ( 15 ), length of a screen on the camera device ( 15 ), width of a screen on the camera device ( 15 ), or a length of a pattern on the camera device ( 15 ).

3. The method according to claim 1 , the length of the camera device ( 15 ) comprises a length of an on-screen digital calibration object ( 30 ) which length is based on the on-screen digital calibration object ( 30 ) on the camera device ( 15 ).

4. The method according to claim 1 , wherein the method uses image recognition, to find a logo, a text, graphics, a length to width ratio, a contour geometry, a lens location, or visible details ( 25 ) present on a camera device ( 15 ) to determine the type of the camera device ( 15 ).

5. A method of performing an absolute distance calibration to a camera device ( 15 ) viewing plane in an image captured in a mirror ( 10 ), the method comprising the steps of:

determining a length of the camera device ( 15 ) based on the type of the camera device ( 15 ),

capturing an image, using the camera device ( 15 ), of the camera device ( 15 ),

determining Field of View, the Field of View registered by meta data or image capturing software, or based on the type of camera device ( 15 ) for a fixed focal length type camera device ( 15 ),

measuring the length of the image of the camera device ( 15 ) from the captured image,

deriving a view angle from the length of the image of the camera device ( 15 ), the total length of the image, and the Field of View angle of the camera device ( 15 ), and

using the view angle and the determined length of the camera device ( 15 ) to calibrate the absolute distance to the camera device ( 15 ) viewing plane.

6. The method according to claim 5 , further comprising steps for performing an absolute angular calibration between a camera device ( 15 ) and a mirror ( 10 ), in an image captured by the camera device ( 15 ), the method comprising the steps of:

capturing an image, using the camera device ( 15 ), of the camera device ( 15 ),

determining Field of View, the Field of View registered by meta data or image capturing software, or based on the type of camera device ( 15 ) for a fixed focal length type camera device ( 15 ),

measuring the length from the center of the image to the image of the camera device ( 15 ) in the captured image, and

deriving the absolute angle calibration between the camera device ( 15 ) and the mirror ( 10 ) from the measured length, the total image length, and the Field of View angle.

7. The method according to claim 6 , further comprising steps for performing an absolute angular calibration of a mirror ( 10 ), where the absolute angular calibration between the camera device ( 15 ) and the mirror ( 10 ) comprises an absolute angular calibration between a camera device ( 15 ) and a mirror ( 10 ) and a registered tilt of the camera device ( 15 ), the tilt by means of a gyroscope or a magnetometer built into the camera device ( 15 ), and the registered tilt is subtracted from the absolute angular calibration between the camera device ( 15 ) and the mirror ( 10 ) to obtain the absolute angular calibration of the mirror ( 10 ).

8. The method of performing an absolute distance calibration to an object ( 20 ) plane according to claim 5 , the absolute distance calibration to the camera device ( 15 ) viewing plane comprises a known distance between an object ( 20 ) plane and a camera device ( 15 ) viewing plane the distance known by instruction to a user ( 5 ), statistical user behavior, or empirical collected data and the distance added to the absolute distance calibration to the camera device ( 15 ) to obtain the absolute distance calibration to the object ( 20 ) plane.

9. The method of performing an absolute distance calibration to an object ( 20 ) plane according to claim 5 , the absolute distance calibration to the camera device ( 15 ) viewing plane, the method comprising creating a vector by:

a known distance between an object ( 20 ) and a camera device ( 15 ), the distance known by instruction to a user ( 5 ), statistical user behavior, or empirical collected data,

the camera device ( 15 ) viewing plane angle relative to a mirror ( 10 ) from the absolute angular calibration angle according to claim 6 ,

a known object plane to a mirror ( 10 ) angle, the angle known by instruction to a user ( 5 ), statistical user behavior, or empirical collected data,

and using the vector and the unit vector of the perpendicular camera device ( 15 ) viewing plane to get a scalar distance, the scalar distance added to the absolute distance calibration to the camera device ( 15 ) to obtain the absolute distance calibration to the object ( 20 ) plane.