Texas Instruments Corporation

Gary Lee

Haydar Bilhan

Ching-Yuh Tsay

Feng Ying

Yong Han

Ramesh Chandrasekaran

M C Ramesh

Gonggui Xu

Lieyi Fang

Xucheng Wang

An image processing apparatus () for a charge coupled device including analog front end circuitry having optical black and offset correction, whereby the offset and optical black correction circuit is programmable. The present invention includes a first circuit () to sample the incoming optical black signal output from a CCD. This first circuit includes a correlated double sampler () coupled to a first programmable gain amplifier (). An adder () connects between the first programmable gain amplifier () and a second gain amplifier () for adding in the optical black offset to the optical black signal input from the CCD. A second circuit () includes a reverse programmable gain amplifier () connected to the output of the second programmable gain amplifier () to amplify the optical black level inversely proportional to the gain from the second programmable gain amplifier (). The second circuit () also includes an integrator () coupled to the reverse programmable gain amplifier () to integrate the difference between the incoming signal and the desired optical black value. The second circuit () couples to the adder () to add the positive and negative difference to the optical black signal. An analog-to-digital converter () converts the sampled signal for further processing at the output of the image processing apparatus ().

Analog optical black clamping circuit for a charge coupled device having wide programmable gain range

A programmable gain amplifier using metal-oxide-semiconductor (MOS) devices to approximate exponential gain characteristic with linear control signals is disclosed. According to one embodiment, the programmable gain amplifier () may include a capacitive switching circuit (), a capacitive switching circuit (), and an operational amplifier (). Capacitive switching circuits (and) may receive an analog input voltage through sample switches (and). Capacitive switching circuit () receives an output from operational amplifier () through feedback switch (). The programmable gain amplifier () may include a few additional unit capacitors which can allow larger gain ranges or more steps for a given range without a large increase in chip size.

Method and apparatus for exponential gain variations with a linearly varying input code

An image processing apparatus for charge coupled device (CCD) and video inputs in a digital camera or for a digital camcorder is disclosed which provides optical black and offset correction for CCD inputs. A sampling circuit, including correlated double sampler (CDS) ( ) and programmable gain amplifier ( ), samples the image input signal and the video input signal. CDS ( ) includes a single-ended amplifier ( ) and a differential amplifier ( ). The single-ended amplifier ( ) functions such that it is only operable during an CCD signal input; otherwise, the single-ended amplifier ( ) is bypassed such that a video signal is only sampled by the differential amplifier ( ). For CCD signals, the single-ended amplifier ( ) samples the reference level of the pixel and holds it during the video interval. The differential amplifier ( ) samples both the output of the single ended amplifier ( ) and the video level of the same pixel. Overall, the CDS ( ) subtracts these levels and converts the difference to a differential output to improve signal to noise performance and dynamic range. An analog-to-digital converter ( ) converts the sampled signal and feeds this digital sample to a digital correction circuit ( ) where optical black level, hot and cold pixels, and line noise are removed.

CMOS analog front end architecture with variable gain for digital cameras and camcorders

A programmable gain amplifier using metal-oxide-semiconductor (MOS) devices to approximate exponential gain characteristic with linear control signals is disclosed. According to one embodiment, the programmable gain amplifier ( ) may include a capacitive switching circuit ( ), a capacitive switching circuit ( ), and an operational amplifier ( ). Capacitive switching circuits ( and ) may receive an analog input voltage through sample switches ( and ). Capacitive switching circuit ( ) receives an output from operational amplifier ( ) through feedback switch ( ). The programmable gain amplifier ( ) may include a few additional unit capacitors which can allow larger gain ranges or more steps for a given range without a large increase in chip size.

A CMOS programmable gain amplifier ( ) is disclosed which provides exponential gain using a single gain element ( ) which may be implemented in either bipolar or CMOS technology. An embodiment of the present invention includes a first and second sampling impedance ( ), a first and second feedback impedance ( ) and a gain element ( ). The gain element ( ) having an inverting input, a non-inverting input and an output. The inverting input connects to the first sampling impedance ( ). The non-inverting input connects to the second sampling impedance ( ). The first feedback impedance ( ) connects between the inverting input and the output. The second feedback impedance ( ) connects between the non-inverting input and the output.

Growing community of inventors

Plano, TX, United States of America

Gary Lee