Measurement And Analysis Of Focal Length And Response Time For The Electrowetting Lens

The electrowetting zoom lens with adjustable focal length are widely used in many fields such as medical,display and camera for their flexibility and long life.The focal length and response time under different driven voltage are the two most important performance parameters of the electrowetting lens.Thus.the measurement of them has been a concern of the researchers.The traditional measurement method of focal length has some shortages such as low precision of focal length,poor adaptability and small measurement range.Therefore,the focal length automated measurement system is designed and developed.Using the Ronchi grating instead of the traditional reticle,the image is not easy to run out of field of view.Meanwhile,With the micro-shooting technology,image processing technology and the stepping motor,the system have higher measurement accuracy.The results of measuring the electrowetting zoom lens by the system show that the repeated measurement accuracy of the system is less than 2% in the range of the focal length from-40 mm to 40 mm.Meanwhile,the hysteresis effect of the electrowetting liquid lens is observed,which means that under the same voltage value,the electrowetting lens has a different focal length during the rising voltage and the dropping voltage drop.Based on the Gaussian beam transmission and lens transformation theory,the response time system is designed and developed,solving the problems such as complexity,low precision,high cost of the traditional method using high speed photography.The mechanism is as follows: the Gaussian beam is still the same beam through the lens.When the focal length of the lens changes,the spatial distribution of the light intensity varies,and the response time of the electrowetting zoom lens can be given according to the change of light intensity detected near the optical axis.The results of measuring the electrowetting zoom lens by the system show that the repeated measurement accuracy of the system is less than 5% by meausing the electrowetting lens.Meanwhile,with the increasing of the voltage,the response time is gradually reduced and stabilized.