Multisampling with reduced bit samples

Abstract

A relatively non-complex signal processor supporting an active pixel sensor imaging system is disclosed. The signal processor only requires the first sample from a group of samples in a multiple sample to be transmitted to the signal processor at full resolution. The subsequent samples in that group can be transmitted using only a subset of least significant bits. The minimum number of required LSBs is based upon the level of noise in the system. In one embodiment, the number of LSBs transmitted is k+2 per sample, where k indicates the number bits corresponding to peak noise. In an alternative embodiment, each subsequent sample is transmitted using only k+1 bits.

What is claimed as new and desired to be protected by letters patent of the united states is:  
     
         1 . A method for transmitting a plurality of digital sample values with reduced bandwidth, comprising: 
 transmitting an entire digital sample value for a first one of said plurality of sample values; and    transmitting a partial digital sample value for each subsequent sample value, each of said partial subsequent digital sample value having at least a predetermined number of least significant bits;    wherein said predetermined number is related to a value of signal noise and is less than the number of bits in said entire digital sample value.    
     
     
         2 . The method of  claim 1 , wherein each subsequent sample is transmitted using a same number of least significant bits.  
     
     
         3 . The method of  claim 1 , wherein said required number is equal to k+1 if said noise is equivalent to a signal having k-bits.  
     
     
         4 . The method of  claim 1 , wherein said required number is equal to k+2 if said noise is equivalent to a signal having k-bits.  
     
     
         5 . A method for receiving a plurality of sample values, comprising: 
 receiving an entire sample value for a first one of said plurality of sample values; and    receiving at least a required number of least significant bits for each subsequent sample value;    wherein said required number is related to a value of signal noise.    
     
     
         6 . The method of  claim 5 , wherein each subsequent sample is transmitted using a same number of least significant bits.  
     
     
         7 . The method of  claim 6 , wherein each subsequent sample is transmitted using the required number of least significant bits.  
     
     
         8 . The method of  claim 5 , wherein said required number is equal to k+1 if said noise is equivalent to a signal having k-bits.  
     
     
         9 . The method of  claim 5 , wherein said required number is equal to k+2 if said noise is equivalent to a signal having k-bits.  
     
     
         10 . The method of  claim 5 , further comprising: for each one of the subsequent plurality of samples, recovering an untransmitted plurality of most significant bits.  
     
     
         11 . A method for recovering information represented by a plurality of untransmitted most significant bits in a subsequent sample of a group of samples where the first transmitted sample of the group is transmitted with full bit resolution and a noise value in the group of samples is equivalent to a k bit signal, said method comprising: 
 if a (k+2)-bit and a (k+1)-bit of the subsequent sample are respectively equal to 0 and 0, and if the (k+2)-bit of a first one of the plurality of samples is equal to 1, setting said untransmitted plurality of most significant bits to be equal to a corresponding set of most significant bits in said first one of the plurality of samples plus one;    otherwise if the (k+2)-bit and (k+1)-bit of the subsequent sample are respectively equal to 1 and 1, and if the (k+2)-bit of the first one of the plurality of samples is equal to 0, setting said untransmitted plurality of most significant bits to be equal the corresponding set of most significant bits in said plurality of samples minus one; and    otherwise setting said untransmitted plurality of most significant bits to be equal to the corresponding set of most significant bits in said first one of the plurality of samples.    
     
     
         12 . A method for recovering information represented by a plurality of untransmitted most significant bits in a subsequent sample of a group of samples where the first transmitted sample of the group is transmitted with fill bit resolution and a noise value in the group of samples is equivalent to a k-bit signal, said method comprising: 
 if a (k+1)-bit and a k-bit of the subsequent sample are respectively equal to 0 and 0, and if a (k+1)-bit and k-bit of a first sample are respectively equal to 1,1, setting said untransmitted plurality of most significant bits to be equal to a corresponding set of most significant bits in said first one of the plurality of samples plus 1;    otherwise if the (k+1)-bit and the k-bit of the subsequent sample are respectively equal to 0 and 1, and if the (k+1)-bit, k-bit, and (k−1)-bit are respectively equal to 1, 1, and 1, setting said untransmitted plurality of most significant bits to be equal to a corresponding set of most significant bits in said first one of the plurality of samples plus 1;    otherwise if the (k+1)-bit and the k-bit of the subsequent sample are respectively equal to 1 and 0, and if the (k+1)-bit, k-bit, and (k−1)-bit are respectively equal to 0, 0, and 0, setting said untransmitted plurality of most significant bits to be equal to a corresponding set of most significant bits in said first one of the plurality of samples minus 1;    otherwise if the (k+1)-bit and the k-bit of the subsequent sample are respectively equal to 1 and 1, and if the (k+1)-bit, and k-bit are respectively equal to 0 and 0, setting said untransmitted plurality of most significant bits to be equal to a corresponding set of most significant bits in said first one of the plurality of samples minus 1;    otherwise if the (k+1)-bit and the k-bit of the subsequent sample are respectively equal to 1 and 1, and if the (k+1)-bit, k-bit, and (k−1)-bit are respectively equal to 0, 1, and 0, setting said untransmitted plurality of most significant bits to be equal to a corresponding set of most significant bits in said first one of the plurality of samples minus 1; and    otherwise setting said untransmitted plurality of most significant bits to be equal to the corresponding set of most significant bits in said first one of the plurality of samples.    
     
     
         13 . A method for computing the sum of a plurality of sample values, comprising: 
 calculating a sum of only a same number of least significant bits of each sample value;    calculating a magnitude from a subset of bits of said plurality of sample values;    shifting and zero-filling said magnitude;    combining said sum and said magnitude to produce a least significant bits portion of a result; shifting and zero-filling a most significant bits portion of a first one of said plurality of samples to produce a most significant bits portion of the result; and    forming said sum of a plurality of sample values using said least significant bits portion of the result with said most significant bits portion of the result.    
     
     
         14 . The method of  claim 13 , wherein said same number is equal to k+2, wherein a peak noise of the signal samples can be characterized by a k-bit signal.  
     
     
         15 . The method of  claim 14 , wherein said same number is equal to 5.  
     
     
         16 . The method of  claim 13 , wherein the number of samples is 4.  
     
     
         17 . The method of  claim 13 , wherein each sample is a 10-bit sample.  
     
     
         18 . The method of  claim 13 , wherein said step of calculating a magnitude comprises: setting an intermediate result to zero; 
 for each sample,    if a (k+2)-bit of a first one of said plurality of samples is equal to 0, and if the (k+2)-bit and (k+1) bit are respectively 1 and 1, summing said intermediate result and 1 and storing said sum in said intermediate result; and    setting said magnitude to said intermediate result.    
     
     
         19 . The method of  claim 13 , wherein said magnitude is left shifted and zero filled until said magnitude is 7 bits wide.  
     
     
         20 . The method of  claim 13 , where said step of combining comprises: 
 if a (k+2)-bit of a first of said plurality of samples is equal to 0, subtracting said sum of said same number of least significant bits from magnitude after said shifting and zero-filling; or    if the (k+2)-bit of said first of said plurality of samples is equal to 1, summing said sum of said same number of least significant bits with said magnitude after said shifting and zero-filling.    
     
     
         21 . A signal processor, comprising: 
 a control circuit, wherein    said control circuit receives a transmission of a plurality of samples, said transmission being in a format such that    each bit of a first one of said plurality of samples is in the transmission,    only a least significant bits portion of each subsequent one of said plurality of samples is in the transmission, and said least significant bits portion of each subsequent sample has a same number of least significant bits, said same number being a function of a noise component of said plurality of samples.    
     
     
         22 . The signal processor of  claim 21 , wherein said same number is equal to k+1, wherein peak noise power can be represented as a k-bit signal.  
     
     
         23 . The signal processor of  claim 21 , wherein said same number is equal to k+2, wherein peak noise power can be represented as a k-bit signal.  
     
     
         24 . The signal processor of  claim 21 , said signal processor further comprises: 
 a least significant bits adder, coupled to and controlled by said control circuit;    a magnitude adder, coupled to and controlled by said control circuit;    an intermediate adder, coupled to and controlled by said control circuit; and    a final adder, coupled to and controlled by said control circuit.    
     
     
         25 . The signal processor of  claim 24 , wherein said control circuit causes said least significant bits adder to compute a least significant bits sum as a sum of said least significant bits portion.  
     
     
         26 . The signal processor of  claim 24 , wherein said control circuit compares the least significant bits portion of said first one of said plurality of samples with the least significant bits portion of each one of said plurality of samples, and produces a magnitude bit for each one of said plurality of samples, and causes said magnitude adder to produce a magnitude sum by summing each of said magnitude bits.  
     
     
         27 . The signal processor of  claim 26 , wherein said controller causes one of said at least one shifter to produce a shifted magnitude sum by shifting and zero filling least significant bits of said magnitude sum.  
     
     
         28 . The signal processor of  claim 27 , wherein said intermediate adder is used to produce a first intermediate result from said shifted magnitude sum and said least significant bits sum.  
     
     
         29 . The signal processor of  claim 28 , wherein said control circuit causes one of said at least one shifter to produce a second intermediate result by shifting and zero filling least significant bits of a most significant bits portion of said first of said plurality of samples.  
     
     
         30 . The signal processor of  claim 29 , wherein said control circuit causes said final adder to produce a sum of said plurality of samples from said first intermediate result and said second intermediate result.  
     
     
         31 . An imaging system comprising: 
 a pixel array that receives an image and provides output signals indicating pixel values resulting from the image;    a sample-and-hold circuit that receives and stores output signals from the pixel array;    an analog-to-digital converter, that receives stored output signals from the sample-and-hold circuit and obtains, for each output signal, a digital value;    a buffer that receives and stores digital values from the analog-to-digital converter; and    a signal processor, including a control circuit which receives digital value from said buffer, in a format wherein each bit of a first one of said plurality of samples is in the transmission, only a least significant bits portion of each subsequent one of said plurality of samples is in the transmission, and said least significant bits portion of each subsequent sample has a same number of least significant bits, said same number being a function of noise within said stored digital values.    
     
     
         32 . The imaging system of  claim 31 , wherein said same number is equal to k+1, wherein peak noise power can be represented as a k-bit signal.  
     
     
         33 . The imaging system of  claim 31 , wherein said same number is equal to k+2, wherein peak noise power can be represented as a k-bit signal.  
     
     
         34 . The imaging system of  claim 31 , wherein said signal processor further comprises, 
 a least significant bits adder, coupled to and controlled by said control circuit;    a magnitude adder, coupled to and controlled by said control circuit;    an intermediate adder, coupled to and controlled by said control circuit; and    a final adder, coupled to and controlled by said control circuit.    
     
     
         35 . The imaging system of  claim 34 , wherein said control circuit causes said least significant bits adder to compute a least significant bits sum as a sum of said least significant bits portion.  
     
     
         36 . The imaging system of  claim 35 , wherein said control circuit compares the least significant bits portion of said first one of said plurality of samples with the least significant bits portion of each one of said plurality of samples, and produces a magnitude bit for each one of said plurality of samples, and causes said magnitude adder to produce a magnitude sum by summing each of said magnitude bits.  
     
     
         37 . The imaging system of  claim 36 , wherein said controller causes one of said at least one shifter to produce a shifted magnitude sum by shifting and zero filling least significant bits of said magnitude sum.  
     
     
         38 . The imaging system of  claim 37 , wherein said intermediate adder is used to produce a first intermediate result from said shifted magnitude sum and said least significant bits sum.  
     
     
         39 . The imaging system of  claim 38 , wherein said control circuit causes one of said at least one shifter to produce a second intermediate result by shifting and zero filling least significant bits of a most significant bits portion of said first of said plurality of samples.  
     
     
         40 . The imaging system of  claim 39 , wherein said control circuit causes said final adder to produce a sum of said plurality of samples from said first intermediate result and said second intermediate result.  
     
     
         41 . The imaging system of  claim 41 , wherein said imaging system is embodied on a single integrated circuit.  
     
     
         42 . The imaging system of  claim 36 , wherein said imaging system is embodied as part of a peripheral device.  
     
     
         43 . A method for sampling a plurality of values, each having N bits, the values indicating a sensed input, comprising: 
 sampling all N bits of a first value; for a subsequent value, sampling M least significant bits where M is less than N; and combining the N bits of the first value with the M bits of the subsequent value to obtain an average value for the sensed input.    
     
     
         44 . A method for processing multiple digital samples of a pixel signal, said method comprising: 
 receiving all bits of one of said multiple digital samples;    receiving a predetermined number of least significant bits of the remaining ones of said multiple digital samples, said predetermined number being related to the magnitude of signal difference among said multiple digital samples; and    processing said received bits to produce a digital signal representing a combination of said multiple digital samples.    
     
     
         45 . A method for recovering information represented by a plurality of untransmitted most significant bits in a subsequent sample of a group of samples where the first transmitted sample of the group is transmitted with full bit resolution and a noise value in the group of samples is equivalent to a k-bit signal, said method comprising: 
 subtracting from the transmitted portion of a subsequent sample a corresponding portion of the first transmitted sample to arrive at an intermediate result;    recovering the untransmitted portion of the subsequent sample as being equal to the corresponding portion of the first transmitted sample if the intermediate result is less than the maximum value of a k-bit signal and greater than the minimum value of negative one times the maximum value of a k-bit signal;    recovering the untransmitted portion of the subsequent sample as being equal to the corresponding portion of the first transmitted sample minus one if the intermediate result is greater than the maximum value of a k-bit signal; and    recovering the untransmitted portion of the subsequent sample as being equal to the corresponding portion of the first transmitted sample plus one if the intermediate result is less than negative one times the maximum value of a k-bit signal.