Image sensor ADC and CDS per column
First Claim
1. Arrangement for converting analog pixel values from an array of pixels to a digital video signal, said array comprising a plurality of columns and at least one row, each column having at one pixel therein, and each column providing a respective pixel value;
- the arrangement comprisinga source of clock signals;
an N-bit counter coupled to said source of clock signals;
an N-bit DAC connected to said counter and having a ramp output providing a signal corresponding to a count existing on said counter;
a plurality of digital counter/latch elements each associated with a respective one of said columns and each also coupled to said source of clock signals;
a plurality of comparators each associated with a respective one of said columns, and having one input connected to receive the respective column pixel value, another input connected to the ramp output of said N-bit counter, and a comparator output connected to a gating terminal of the respective digital counter/latch element;
a video readout bus; and
means selectively transferring contents of said digital counter/latch elements to said video output bus to produce said digital video signal.
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Accused Products
Abstract
A solid state imager converts analog pixel values to digital form on an arrayed per-column basis. An N-bit counter supplies an N-bit DAC to produce an analog ramp output with a level that varies corresponding to the contents of the counter. A ripple counter or equivalent is associated with each respective column. A clock supplies clock signals to the counter elements. A comparator in each column gates the counter element when the analog ramp equals the pixel value for that column. The contents of the counters are transferred sequentially to a video output bus to produce the digital video signal. Additional black-level readout counter elements can create and store a digital value that corresponds to a dark or black video level. A subtraction element subtracts the black level value from the pixel value to reduce fixed pattern noise. An additional array of buffer counter/latches can be employed. The ripple counters can be configured as counters to capture the digital video level, and then as shift registers to clock out the video levels to an output bus. The clock pulses for the DAC counter and for the ripple counters can be at the same or different rates.
24 Citations
15 Claims
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1. Arrangement for converting analog pixel values from an array of pixels to a digital video signal, said array comprising a plurality of columns and at least one row, each column having at one pixel therein, and each column providing a respective pixel value;
- the arrangement comprising
a source of clock signals; an N-bit counter coupled to said source of clock signals; an N-bit DAC connected to said counter and having a ramp output providing a signal corresponding to a count existing on said counter; a plurality of digital counter/latch elements each associated with a respective one of said columns and each also coupled to said source of clock signals; a plurality of comparators each associated with a respective one of said columns, and having one input connected to receive the respective column pixel value, another input connected to the ramp output of said N-bit counter, and a comparator output connected to a gating terminal of the respective digital counter/latch element; a video readout bus; and means selectively transferring contents of said digital counter/latch elements to said video output bus to produce said digital video signal. - View Dependent Claims (2, 3, 4, 5, 6)
- the arrangement comprising
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7. Arrangement for converting analog pixel values from an array of pixels to a digital video signal, said array comprising a plurality of columns and at least one row, each column having at one pixel therein, and each column providing a respective pixel value;
- the arrangement comprising an N-bit counter;
an N-bit DAC connected to said counter and having a ramp output providing a signal corresponding to a count existing on said counter;
a plurality of digital latch/counter elements each associated with a respective one of said columns;
a plurality of comparators each associated with a respective one of said columns, said latch/counter elements having an input elements to receive clock pulses and also being coupled to the associated comparator;
wherein each comparator is made up of a differential-input amplifier, each of the amplifiers having a plurality of at least the first input transistor(s), one of the first input transistors located at each of the pixels with in the periphery, and a second input transistor located outside the periphery of the array and coupled to the first input transistors and to an output configuration circuit, and having one input connected to receive the respective column pixel value, another input connected to the ramp output of said N-bit DAC, and a comparator output connected to a gating terminal of the respective digital latch/counter element;
a video readout bus; and
means selectively transferring contents of said digital latch/counter elements to said video output bus to produce said digital video signal. - View Dependent Claims (8, 9, 10, 11, 12)
- the arrangement comprising an N-bit counter;
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13. Arrangement for converting analog pixel values from an array of pixels to a digital video signal, said array comprising a plurality of columns and at least one row, each column having at one pixel therein, and each column providing a respective pixel value;
- the arrangement comprising
a source of clock signals; an N-bit counter coupled to said source of clock signals; an N-bit DAC connected to said counter and having a ramp output providing a signal corresponding to a count existing on said counter; a plurality of digital counter/latch elements each associated with a respective one of said columns and each also coupled to said source of clock signals; a plurality of comparators each associated with a respective one of said columns, and having one input connected to receive the respective column pixel value, another input connected to the ramp output of said N-bit counter, and a comparator output connected to a gating terminal of the respective digital counter/latch element; and wherein each said digital counter/latch element is formed of a plurality of flip-flops including control inputs to receive a LATCH signal and a READ OUT signal, respectively, such that when said LATCH signal is applied the digital counter/latch elements count said clock signals to store a value corresponding to the respective pixel value, and when said READ OUT signal is applied said digital counter/latch elements are configured as a shift register and serve as means sequentially transferring contents of said digital counter/latch elements to a video output bus to produce said digital video signal. - View Dependent Claims (14, 15)
- the arrangement comprising
Specification