Sensor-assisted autofocus calibration
A mobile device includes a camera module, including a lens and an image sensor. An inertial sensor in the mobile device outputs a signal indicative of an orientation of the device. A controller corrects one or more focal properties of the camera module responsively to the orientation indicated by the inertial sensor.
1. A mobile device, comprising:
a camera module, comprising a lens and an image sensor that lie along a focal axis;
an inertial sensor, which is configured to output a signal indicative of an orientation of the device; and
a controller, which is configured to correct for a displacement, between the lens and the image sensor, in a direction that is transverse to the focal axis, caused by a change in a direction of gravitational pull on components of the camera module that results from the mobile device being turned on its side, responsively to:
the signal from the inertial sensor indicating that the mobile device is being held on its side, and
stored values indicative of a dependence of the displacement on the orientation.
2. The device according to claim 1 , and comprising a temperature sensor, wherein the controller is configured to correct for the displacement responsively to a temperature indicated by the temperature sensor.
3. The device according to claim 1 , wherein the controller is configured to correct for the displacement by processing electronic images output by the camera module.
4. The device according to claim 1 , wherein the controller is further configured to correct, responsively to the orientation indicated by the signal from the inertial sensor, for a deviation in a distance, along the focal axis, between the lens and the image sensor.
5. The device according to claim 4 , wherein the controller is configured to correct for the deviation by adjusting the distance between the lens and the image sensor.
6. The device according to claim 5 , wherein the camera module comprises an autofocus mechanism, and wherein the controller is configured to adjust the autofocus mechanism responsively to the orientation in order to correct for the deviation in the distance between the lens and the image sensor.
7. The device according to claim 1 , wherein the stored values include tables of values of the displacement for different orientation angles of the device.
8. The device according to claim 1 , wherein the stored values include constants derived by fitting a function to calibration measurements of the displacement.
9. The device according to claim 1 , wherein the stored values indicate, for the orientation indicated by the signal from the inertial sensor, a corresponding deviation in a position of a center of the image sensor, and wherein the controller is configured to correct for the displacement by using the stored values to determine the deviation.
10. The device according to claim 1 , wherein the stored values include calibration parameters that were derived by finding a transverse shift of an image of a target relative to a known reference image of the target.
11. A method for imaging, comprising:
capturing electronic images using a camera module in a mobile device, the camera module comprising a lens and an image sensor that lie along a focal axis;
receiving, from an inertial sensor in the mobile device, a signal indicative of an orientation of the device; and
correcting for a displacement, between the lens and the image sensor, in a direction that is transverse to the focal axis, caused by a change in a direction of gravitational pull on components of the camera module that results from the mobile device being turned on its side, responsively to:
the signal from the inertial sensor indicating that the mobile device is being held on its side, and
stored values indicative of a dependence of the displacement on the orientation.
12. The method according to claim 11 , wherein the mobile device comprises a temperature sensor, and wherein correcting for the displacement comprises correcting for the displacement responsively to a temperature indicated by the temperature sensor.
13. The method according to claim 11 , wherein correcting for the displacement comprises processing electronic images output by the camera module.
14. The method according to claim 11 , further comprising, responsively to the orientation indicated by the signal from the inertial sensor, correcting for a deviation in a distance, along the focal axis, between the lens and the image sensor.
15. The method according to claim 14 , wherein correcting for the deviation comprises correcting the distance between the lens and the image sensor.
16. The method according to claim 15 , wherein the camera module comprises an autofocus mechanism, and wherein correcting the distance comprises adjusting the autofocus mechanism responsively to the orientation.
17. The method according to claim 11 , wherein the stored values include tables of values of the displacement for different orientation angles of the device.
18. The method according to claim 11 , wherein the stored values include constants derived by fitting a function to calibration measurements of the displacement.
19. The method according to claim 11 , wherein the stored values indicate, for the orientation indicated by the signal from the inertial sensor, a corresponding deviation in a position of a center of the image sensor, and wherein correcting for the displacement comprises correcting for the displacement by using the stored values to determine the deviation.
20. The method according to claim 11 , wherein the stored values include calibration parameters that were derived by finding a transverse shift of an image of a target relative to a known reference image of the target.