Infrared imager readout electronics

Abstract

Readout integrated circuits placed underneath the suspended sensing elements detect changes of electrical resistance of sensing elements and digitize the signals with digital to analog convertor for each element. Readout electronics provides low parasitics, high signal to noise ratio, high data rate, high dynamic range and instantaneous global readout.

What is claimed is: 
     
         1 . A method of reading out a resistance of a sensor in an array of sensors without perturbing an integration process comprising:
 Providing a readout integrated circuit monolithically integrated with the sensor wherein the readout integrated circuit comprises a constant voltage source, an integration capacitor and a source follower;   Applying the constant voltage to the sensor using the constant voltage source;   Accumulating resulting charge passed through the sensor on the integration capacitor;   Sampling the voltage on the integration capacitor using the source follower thereby not affecting charge accumulation in the integration capacitor.   
     
     
         2 . The method of  claim 1  which repeats the sampling process multiple times within a single integration period. 
     
     
         3 . The method of  claim 1  which expands the dynamic range of a readout of the array of sensors comprising:
 Providing an analog to digital converter; 
 Sampling the voltage on the integration capacitor at the beginning of an integration cycle; 
 Determining sampling time schedule based on the voltages of the initial sampling; 
 Determining a digital to analog converter voltage for the array based on the voltages of the initial sampling of sensors in the array; 
 Adjusting the number of samples for those sensors having a rate of change of the storage capacitor voltage within a region of interest. 
 Constructing an image composed of the readout signals of the array of sensors with digital to analog converter voltages adjusted for different integration times in a single image frame. 
 
     
     
         4 . The method of  claim 1  which compensates for sensor to sensor variation comprising:
 Providing a non-volatile memory; 
 Determining resistance and sensitivity of each sensor in the array; 
 Determining presence and location of nonfunctional sensors in the array; 
 Storing the location of nonfunctional sensors in the non-volatile memory; 
 Storing the resistance and sensitivity values in the non-volatile memory; 
 Compensating for variations in resistance and sensitivity by adjusting offset and gain for each sensor; 
 Applying an algorithm to interpolate signals for nonfunctional sensors using signals of neighboring functioning sensors. 
 
     
     
         5 . The method of  claim 1  that provides global shutter functionality comprising:
 Providing a storage capacitor and an analog to digital converter; 
 Storing the source follower output of each sensor in the array in the associated storage capacitor globally and simultaneously; 
 Reading out the voltage stored on the storage capacitor with the analog to digital converter. 
 
     
     
         6 . The method of  claim 1  that reduces 1/f noise and fixed pattern noise comprising:
 Taking two samples of the integration capacitor voltage sequentially; 
 Subtracting the first sample from the subsequent sample. 
 
     
     
         7 . A method of performing analog to digital conversion and readout for a sensor in an array of sensors comprising:
 Providing a readout integrated circuit monolithically integrated with the sensor wherein the readout integrated circuit comprises a comparator;   Providing a digital to analog converter, a bit line, and a sense amplifier;   Sampling an analog voltage from the sensor;   Performing the comparator operation between the analog voltage and the signal from the digital to analog converter for sensors in the array in parallel;   Passing the digital comparator output to the bit line;   Reading out the digital signal on the bit line with the sense amplifier.   
     
     
         8 . The method of  claim 7  that performs analog to digital conversion and readout for a sensor in an array of sensors comprising:
 Providing a storage capacitor; 
 Storing the analog voltage from the sensor on the storage capacitor; 
 Performing the comparator operation between the voltage on the storage capacitor and the signal from the digital to analog converter for sensors in the array in parallel; 
 Passing the digital comparator output to the bit line; 
 Reading out the digital signal on the bit line with the sense amplifier. 
 
     
     
         9 . A method of reading out a resistance of a sensor in an array of sensors:
 Providing a readout integrated circuit monolithically integrated with the sensor wherein the readout integrated circuit comprises a constant current source, and a storage capacitor;   Applying the constant current to the sensor using the constant current source;   Sampling a resulting instantaneous voltage on the sensor;   Storing the instantaneous voltage in the storage capacitor;   
     
     
         10 . The method of  claim 9  which repeats the sampling process multiple times within a single frame. 
     
     
         11 . The method of  claim 9  which expands the dynamic range of a readout of the array of sensors comprising:
 Providing an analog to digital converter; 
 Sampling the voltage on the storage capacitor at the beginning of an integration cycle; 
 Determining sampling time schedule based on the voltages of the initial sampling; 
 Determining a digital to analog converter voltage for the array based on the voltages of the initial sampling of sensors in the array; 
 Adjusting the number of samples for those sensors having a rate of change of the storage capacitor voltage within a region of interest. 
 Constructing an image composed of the readout signals of the array of sensors with digital to analog converter voltages adjusted for different integration times in a single image frame. 
 
     
     
         12 . The method of  claim 9  which compensates for sensor to sensor variation comprising:
 Providing a non-volatile memory; 
 Determining resistance and sensitivity of each sensor in the array; 
 Determining presence and location of nonfunctional sensors in the array; 
 Storing the resistance and sensitivity values in the non-volatile memory; 
 Storing the location of nonfunctional sensors in the non-volatile memory; 
 Compensating for variations in resistance and sensitivity by adjusting the offset and gain for each sensor; 
 Applying an algorithm to interpolate signals for nonfunctional sensors using signals of neighboring functioning sensors. 
 
     
     
         13 . The method of  claim 9  that provides global shutter functionality comprising:
 Providing an analog to digital converter; 
 Sampling and holding the voltage on the sensor globally and simultaneously in the storage capacitor; 
 Reading out the voltage stored in the storage capacitor with the analog to digital converter. 
 
     
     
         14 . The method of  claim 9  that reduces 1/f noise and fixed pattern noise comprising:
 Taking two samples of the integration capacitor voltage sequentially; 
 Subtracting the first sample from the subsequent sample. 
 
     
     
         15 . The method of  claim 1  further comprising:
 Exposing the sensor to electromagnetic radiation; 
 Determining intensity of electromagnetic radiation based on changes of the sensor resistance before and after exposure to electromagnetic radiation. 
 
     
     
         16 . The method of  claim 7  further comprising:
 Exposing the sensor to electromagnetic radiation; 
 Determining intensity of electromagnetic radiation based on changes of the sensor resistance before and after exposure to electromagnetic radiation. 
 
     
     
         17 . The method of  claim 9  further comprising:
 Exposing the sensor to electromagnetic radiation; 
 Determining intensity of electromagnetic radiation based on changes of the sensor resistance before and after exposure to electromagnetic radiation. 
 
     
     
         18 . The method of  claim 1  further comprising:
 Providing optical elements and an image processor; 
 Applying algorithms to the readout sensor resistances to enable motion tracking and gesture recognition. 
 
     
     
         19 . The method of  claim 7  further comprising:
 Providing optical elements and an image processor; 
 Applying algorithms to the readout sensor resistances to enable motion tracking and gesture recognition. 
 
     
     
         20 . The method of  claim 9  further comprising:
 Providing optical elements and an image processor; 
 Applying algorithms to the readout sensor resistances to enable motion tracking and gesture recognition.