초록 ▼

A system and method for estimating lens temperature is disclosed. In one embodiment, a camera comprises a body and a lens assembly. The lens assembly comprises a focus mechanism. The body comprises a heat generating element, a sensor proximally located to the heat generating element, and a processor

A system and method for estimating lens temperature is disclosed. In one embodiment, a camera comprises a body and a lens assembly. The lens assembly comprises a focus mechanism. The body comprises a heat generating element, a sensor proximally located to the heat generating element, and a processor. The sensor is configured to provide a signal responsive to temperature. The processor is configured to apply an input responsive to the signal to a heat transfer model to determine a temperature of the lens assembly. The processor further determines a focus error correction responsive to the temperature of said lens assembly.

대표청구항 ▼

1. A method for estimating the temperature of a camera lens, comprising:sensing temperature at a location within the body of a camera;monitoring the occurrence and duration of on/off operating states of heat generating elements of the camera; andusing the temperature at a location within the body of

1. A method for estimating the temperature of a camera lens, comprising:sensing temperature at a location within the body of a camera;monitoring the occurrence and duration of on/off operating states of heat generating elements of the camera; andusing the temperature at a location within the body of the camera and monitored occurrence and duration of on/off operating states of heat generating elements within the camera body to determine a current temperature of a lens assembly coupled to the camera. 2. The method of claim 1, further comprising:correcting temperature induced focus error in accordance with the current temperature of the lens assembly. 3. The method of claim 1, wherein using the temperature at a location within the body of the camera and monitored occurrence and duration of on/off operating states to determine a current temperature of a lens assembly comprises using a model to estimate temperature of the lens assembly as a function of time. 4. The method of claim 3, wherein using a model to estimate temperature comprises determining a time constant for each combination of heat generating elements. 5. The method of claim 3, wherein the model is a mathematical model of heat transfer effects from the body of the camera to the lens assembly. 6. The method of claim 3, wherein the model is generated responsive to empirical data. 7. The method of claim 3, wherein the model is generated responsive to calculation. 8. The method of claim 1, wherein using the temperature at a location within the body of the camera and monitored occurrence and duration of on/off operating states to determine a current temperature of a lens assembly comprises associating the occurrence of operating state changes with time stamps. 9. The method of claim 1, wherein correcting temperature induced focus error comprises determining the number of focus position steps to reposition a focus mechanism. 10. The method of claim 9, wherein determining the number of focus position steps comprises determining a difference between the current temperature of a lens assembly and a temperature of the lens assembly when the focus mechanism of the camera was calibrated. 11. A system, comprising:means for measuring at least one temperature within the body of a camera;means for determining the occurrence of on/off state changes of heat generating elements within the camera;means for determining an elapsed time since a last on/off state change;means for estimating the temperature of a lens assembly coupled to the camera responsive to the on/off state of heat generating elements within the camera and an elapsed time since a last on/off state change;means for correcting temperature induced focus error in accordance with the estimated temperature of the lens assembly. 12. The system of claim 11, wherein said means for estimating the temperature of a lens assembly coupled to the camera comprises a means for calculating an ambient temperature. 13. The system of claim 11, wherein said means for estimating the temperature of a lens assembly coupled to the camera comprises applying a time constant to a model. 14. The system of claim 11, wherein said means for adjusting temperature induced focus error comprises determining the number of focus position steps to traverse when adjusting a focus mechanism. 15. The system of claim 14, wherein determining the number of focus position steps to traverse when adjusting a focus mechanism is responsive to a temperature offset from a lens assembly temperature when the focus mechanism was calibrated. 16. A camera, comprising:a heat generating element within a body of said camera;a sensor proximally located to said heat generating element, said sensor configured to provide a signal responsive to temperature;a lens assembly coupled to said camera, said lens assembly including a focus mechanism; anda processor configured to apply an input responsive to said signal to a heat transfer model to determine a temperature of said lens assembly, wherein said processor is further configured to determine a focus error correction responsive to the temperature of said lens assembly. 17. The camera of claim 16, further comprising:a state sensor configured to identify an on/off state responsive to said heat generating element; anda clock configured to associate a timestamp responsive to changes in the on/off state of said heat generating element, wherein the heat transfer model is responsive to the duration since a last occurrence of a change in the on/off state of said heat generating element. 18. The camera of claim 16, wherein the heat transfer model comprises a time constant responsive to said heat generating element. 19. The camera of claim 16, wherein the heat transfer model is responsive to empirical temperature data. 20. The camera of claim 16, wherein the focus error correction is responsive to a temperature of said lens assembly when said focus mechanism was calibrated. 21. The camera of claim 16, wherein the focus error correction directs a focus range applied during an auto-focus process. 22. A computer-readable medium having a program for correcting temperature induced focus error in a camera, the program comprising logic for:recording a first time and a first input responsive to a heat generating element within the body of the camera responsive to said camera being turned off;recording a second time and a second input responsive to the heat generating element responsive to said camera being turned on;estimating a first lens assembly temperature responsive to an ambient temperature and a lens assembly temperature when said camera was turned off;recording a third time responsive to a shutter input;estimating a present lens assembly temperature responsive to the shutter input; anddetermining a focus range appropriate to apply to the lens assembly to compensate for delta between the present lens assembly temperature and a temperature of the lens assembly when the focus mechanism was calibrated. 23. The computer-readable medium of claim 22, wherein estimating a present lens assembly temperature is responsive to a constant representing the difference between ambient temperature and a steady-state lens assembly temperature. 24. The computer-readable medium of claim 22, wherein estimating a present lens assembly temperature is responsive to a constant representing the difference between ambient temperature and a steady-state input responsive to the heat generating element when the heat generating element is turned on. 25. The computer-readable medium of claim 22, wherein estimating a present lens assembly temperature is responsive to a difference determined from the third time and the second time. 26. The computer-readable medium of claim 22, wherein estimating a present lens assembly temperature is responsive to a lens assembly time constant. 27. The computer-readable medium of claim 26, wherein the lens assembly time constant is derived from empirical data. 28. The computer-readable medium of claim 26, wherein the lens assembly time constant is calculated. 29. The computer-readable medium of claim 22, wherein estimating a present lens assembly temperature is responsive to a heat generating element time constant. 30. The computer-readable medium of claim 29, wherein the heat generating element time constant is derived from empirical data. 31. The computer-readable medium of claim 29, wherein the heat generating element time constant is calculated. 32. The computer-readable medium of claim 22, wherein estimating a present lens assembly temperature is responsive to an ambient temperature. 33. The computer-readable medium of claim 32, wherein the ambient temperature is estimated responsive to the first input responsive to the heat generating element. 34. The computer-readable medium of claim 32, wherein the ambient temperature is estimated responsive to a heat generating element time constant. 35. The computer-readable medium of claim 32, wherein the ambient temperature is estimated responsive to the second input responsive to the heat generating element. 36. The computer-readable medium of claim 32, wherein the ambient temperature is estimated responsive to a difference determined from the second time and the first time.