Apparatus and method for position sensing in MEMS actuators using temperature resistance variations
In the field of micro-electromechanical systems (MEMS) for autofocus camera systems, a MEMS device comprises a fixed part, a movable platform with an image sensor, and temperature sensors on both the platform and fixed part. A processor calculates the temperature difference to determine the platform's displacement. This method eliminates the need for additional capacitive or piezoelectric components, reducing complexity and cost. The described technology is particularly useful in consumer electronics, such as smartphone and automotive cameras, where precise focus control may be vital.
1 . A micro-electromechanical system (MEMS) device comprising:
a fixed part;
a platform suspended above the fixed part, wherein the platform is configured to move relative to the fixed part;
an image sensor disposed on the platform such that it moves with the platform;
a first temperature sensor disposed on either the platform or the image sensor such that the first temperature sensor moves with the platform, wherein the first temperature sensor is configured to measure a first temperature of either the platform or the image sensor;
a second temperature sensor disposed on the fixed part, wherein the second temperature sensor is configured to measure a second temperature of the fixed part; and
a processor communicatively connected to the first temperature sensor and the second temperature sensor, wherein the processor is programmed to (i) determine a temperature difference between the first temperature and the second temperature, and (ii) determine a relative displacement of the platform relative to the fixed part based upon the temperature difference.
2 . The MEMS device of claim 1 , wherein the first temperature sensor is disposed directly on the platform.
3 . The MEMS device of claim 1 , wherein the first temperature sensor is disposed directly on or internal to the image sensor.
4 . The MEMS device of claim 1 , wherein the MEMS device is part of an electrostatic actuator with pistons and tubes.
5 . The MEMS device of claim 1 , wherein the first temperature sensor includes a plurality of discrete temperature sensors dispersed across various locations on the platform.
6 . The MEMS device of claim 5 , wherein the processor is programmed to determine the first temperature based on an average readings from the discrete temperature sensors.
7 . The MEMS device of claim 1 , wherein the platform is suspended via springs configured to allow for movement of the platform.
8 . The MEMS device of claim 1 , wherein the image sensor is disposed directly on the platform.
9 . A micro-electromechanical system (MEMS) device comprising:
a fixed part;
a platform moveable relative to the fixed part;
an image sensor disposed on the platform such that it moves with the platform relative to the fixed part;
a first temperature sensor disposed on the platform such that the first temperature sensor moves with the platform relative to the fixed part, wherein the first temperature sensor is configured to measure a first temperature of the platform;
a second temperature sensor disposed on the fixed part, wherein the second temperature sensor is configured to measure a second temperature of the fixed part; and
a processor communicatively connected to the first temperature sensor and the second temperature sensor, wherein the processor is programmed to determine a relative displacement of the platform relative to the fixed part based upon the first temperature and the second temperature.
10 . The MEMS device of claim 9 , wherein the processor is programmed to (i) determine a temperature difference between the first temperature and the second temperature, and (ii) determine the relative displacement based on the temperature difference.
11 . The MEMS device of claim 9 , wherein the first temperature sensor is disposed directly on the platform.
12 . The MEMS device of claim 9 , wherein the first temperature sensor is disposed directly on the image sensor.
13 . The MEMS device of claim 9 , wherein the MEMS device is part of an electrostatic actuator with pistons and tubes.
14 . The MEMS device of claim 9 , wherein the first temperature sensor includes a plurality of discrete temperature sensors dispersed across various locations on the platform.
15 . The MEMS device of claim 14 , wherein the processor is programmed to determine the first temperature based on an average readings from the discrete temperature sensors.
16 . A method for determining the position of a micro-electromechanical system (MEMS) actuator in a camera system, the method comprising:
receiving a first temperature measurement from a first temperature sensor disposed on a movable platform of the MEMS actuator;
receiving a second temperature measurement from a second temperature sensor disposed on a fixed part of the MEMS actuator;
calculating a temperature difference between the first temperature measurement and the second temperature measurement;
determining a displacement of the movable platform relative to the fixed part based on the calculated temperature difference; and
adjusting the focus of the camera system based on the determined displacement.
17 . The method of claim 16 , wherein the first temperature sensor disposed directly on the movable platform.
18 . The method of claim 16 , wherein the first temperature sensor includes a plurality of discrete temperature sensors dispersed across various locations on the movable platform, wherein the first temperature measurement corresponds to an average of temperature measurements output by the plurality of discrete temperature sensors.
19 . The method of claim 18 , wherein the discrete temperature sensors are located at corners of the movable platform.
20 . The method of claim 16 , wherein the platform is suspended via springs configured to isolate vibrations and allow for movement of the platform.