Dynamic range extender apparatus, system, and method for digital image receiver system
AssigneeCirrus Logic, Inc.
InventorsSandra M. Johnson, Nadi R. Itani
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Abstract
A dynamic range enhancement system (DRES) receives input signals from an imager device connected to a correlated double sampling (CDS) circuit for receiving the video signal from the CCD imaging device. The dynamic range enhancement system includes a variable gain amplifier (VGA), and a limited bit-width analog-to-digital converter (ADC) which digitizes the analog signal received from the VGA. The output of the ADC is provided to an initial bit range position of a wider bit-width shifter connected to the output of the ADC. The DRES system includes a 2-bit ADC for extending the dynamic range of the imager device, which enhances the dynamic range of a 10 bit ADC to 13 bits.
Claims29
A method of extending the dynamic range of an electrical system including a variable gain amplifier connected to an analog-to-digital converter producing an output signal of predetermined bit-width, said method comprising:
- receiving an analog signal of particular temporal magnitude;
- amplifying the received analog signal by a first gain value;
- changing said first gain value to a second gain value as a function of the temporal magnitude of the received analog signal;
- converting the analog signal into a counterpart digital signal of predetermined bit-width;
- and
- adjusting the bit-width of the counterpart digital signal to compensate for a change in amplification provided by said variable gain amplifier.
A processing system for an imager device comprising:
- a camera system for producing an imager signal;
- a correlated double sampling circuit for receiving data from an imager;
- a variable gain amplifier connected to said correlated double sampling circuit, for receiving the sampled output of the correlated double sampling circuit;
- an analog-to-digital converter (ADC) coupled to said variable gain amplifier;
- a shifter for holding a bit sequence of predetermined length, said shifter connected to the output of said ADC;
- and
- a control circuit coupled to the output of said correlated double sampling circuit and adapted to control the amplification setting of said variable gain amplifier, and to control the shift status of bits in said shifter.
A method of extending the dynamic range of an imaging system having a correlated double sampling system, a variable gain amplifier circuit connected to said correlated double sampling system, an analog-to digital converter connected to said variable gain amplifier circuit, and a shifter containing a predetermined number of bits greater than the digital output width of said analog-to-digital converter, said shifter connected to said analog-to-digital converter for receiving the output bit set of said analog-to-digital converter into predetermined locations in said shifter, including:
- determining the magnitude of input signals from an imaging system, which are sampled by a correlated double sampling system;
- adjusting the gain in a variable gain amplifier in a selected direction;
- and
- repositioning the bit set stored in said shifter in an opposite direction from the gain direction expressed upon said variable gain amplifier, to produce a digital output of greater dynamic range from said shifter than from said analog-to-digital converter.
A method of calibrating a dynamic range expandable imaging system having a correlated double sampling system, a variable gain amplifier circuit connected to said correlated double sampling system, an analog-to digital converter connected to said variable gain amplifier circuit, and a shifter containing a predetermined number of bits greater than the digital output width of said analog-to-digital converter, said shifter connected to said analog-to-digital converter for receiving the output bit set of said analog-to-digital converter into predetermined locations in said shifter, including:
- injecting input test signals from a predetermined input circuit for sampling by a correlated double sampling system, above and below a first trip point in VGA input values at which VGA gain shifts have been determined;
- determining the difference in analog-to-digital converter output corresponding to said first trip point;
- injecting input test signals from a predetermined input circuit for sampling by a correlated double sampling system, above and below a next trip point in VGA input values at which VGA gain shifts have been determined;
- and
- determining the difference in analog-to-digital converter output corresponding to said next trip point.
A processing system for an imager device comprising:
- a camera system for producing an imager signal;
- a correlated double sampling (CDS) circuit for receiving data from an imager;
- a variable gain amplifier connected to said correlated double sampling circuit, for receiving the sampled output of the correlated double sampling circuit;
- an analog-to-digital converter (ADC) coupled to said variable gain amplifier;
- an offset injection mechanism (OIM) connected to said ADC for adjusting the output of said ADC;
- a shifter for holding a bit sequence of predetermined length, said shifter connected to said OIM;
- a control circuit coupled to the output of said correlated double sampling circuit and adapted to control the amplification setting of said variable gain amplifier, and to control the shift status of bits in said shifter.
A method to use an abbreviated bit ADC with a VGA and a simple small ADC to extend the dynamic range of the output while still maintaining low quantization noise at the low end of the signal range.
A method of dynamic range extension with minimal increase of power and silicon area.
A method of calibrating the dynamic range extension circuit to remove any discontinuities that can be caused by gain switching in the analog domain which does not exactly match the gain switching in the digital domain.
Dependencies are inferred from the claim text.