Systems and methods reduce temperature induced drift effects on a liquid lens
Systems and methods reduce temperature induced drift effects on a liquid lens used in a vision system. A feedback loop receives a temperature value from a temperature sensor, and based on the received temperature value, controls a power to the heating element based on a difference between the measured temperature of the liquid lens and a predetermined control temperature to maintain the temperature value within a predetermined control temperature range to reduce the effects of drift. A processor can also control a bias signal applied to the lens or a lens actuator to control temperature variations and the associated induced drift effects. An image sharpness can also be determined over a series of images, alone or in combination with controlling the temperature of the liquid lens, to adjust a focal distance of the lens.
1. A vision system comprising:
an adjustable focus liquid lens having a field of view;
at least one circuit board in thermal contact with at least a portion of the liquid lens;
a heating element positioned on the at least one circuit board, the heating element controllable to heat the at least one circuit board;
a temperature sensor positioned to measure a temperature of the liquid lens; and
a feedback loop, the feedback loop to control a power to the heating element based on a difference between the measured temperature of the liquid lens and a predetermined control temperature.
2. The vision system according to claim 1 , further including a processor, the processor to receive a temperature value from the temperature sensor, and based on the received temperature value, energize or de-energize the heating element on the at least one circuit board to maintain the temperature value within a predetermined control temperature range.
3. The vision system according to claim 1 , wherein the predetermined control temperature is near a high end of the operating temperature range of the liquid lens.
4. The vision system according to claim 1 , wherein the temperature sensor is positioned on the at least one circuit board.
5. The vision system according to claim 1 , wherein the at least one circuit board includes liquid lens driver circuitry.
6. The vision system according to claim 1 , wherein the at least one circuit board includes vision system control circuitry.
7. The vision system according to claim 1 , further including a second circuit board.
8. The vision system according to claim 1 , wherein the focus of the adjustable focus liquid lens is adjustable with a control signal applied to the liquid lens.
9. The vision system according to claim 1 , wherein the vision system is at least one of a fixed mount vision system and a hand-held vision system.