Patent ID: 7889249
Filing Date: 2011-02-15
Classification: G01J,H04N

Abstract:
1. A color sensor configured to sense a plurality of color components of light incident thereon, comprising: a Red color sensor circuit comprising a Red photodetector configured to receive the incident light thereon and provide a Red photocurrent therefrom, to a Red transimpedance amplifier as an input thereto in response to the incident light. the Red transimpedance amplifier being configured to provide a Red output voltage indicative of a Red intensity of a Red spectrum included in the incident light as the Red intensity occurs under a present operating temperature, the Red transimpedance amplifier further comprising a Red feedback resistor component arranged in parallel with a Red compensation capacitor, the Red feedback resistor component and the Red compensation capacitor having values selected to permit accurate measurement of the Red intensity, a first slope of a voltage response of the Red transimpedance amplifier not varying with temperature; a Green color sensor circuit comprising a Green photodetector configured to receive the incident light thereon and provide a Green photocurrent therefrom to a Green transimpedance amplifier as an input thereto in response to the incident light, the Green transimpedance amplifier being configured to provide a Green output voltage indicative of a Green intensity of a Green spectrum included in the incident light as the Green intensity occurs under the present operating temperature, the Green transimpedance amplifier further comprising a Green feedback resistor component arranged in parallel with a Green compensation capacitor, the Green feedback resistor component and the Green compensation capacitor having values selected to permit accurate measurement of the Green intensity, a second slope of a voltage response of the Green transimpedance amplifier not varying with temperature: a Blue color sensor circuit comprising a Blue photodetector configured to receive the incident light thereon and provide a Blue photocurrent therefrom to a Blue transimpedance amplifier as an input thereto in response to the incident light, the Blue transimpedance amplifier being configured to provide a Blue output voltage indicative of a Blue intensity of a Blue spectrum included in the incident light as the Blue intensity occurs under the present operating temperature, the Blue transimpedance amplifier further comprising a Blue feedback resistor component arranged in parallel with a Blue compensation capacitor, the Blue feedback resistor component and the Blue compensation capacitor having values selected to permit accurate measurement of the Blue intensity, a third slope of a voltage response of the Blue transimpedance amplifier not varying with temperature; a dark color sensor circuit comprising a dark photodetector configured to provide a dark photocurrent proportional to the present operating temperature to a dark color transimpedance amplifier as an input thereto, the dark color transimpedance amplifier converting the dark photocurrent into a dark current offset voltage, the dark color transimpedance amplifier further comprising a dark feedback resistor component arranged in parallel with a dark compensation capacitor, the dark feedback resistor component and the dark compensation capacitor having values selected to permit accurate measurement of the dark photocurrent, a fourth slope of a voltage response of the dark color transimpedance amplifier not varying with temperature; a Red differential amplifier configured to receive the Red output voltage and the dark current offset voltage as inputs thereto and configured to use the dark current offset voltage to cancel the contribution of the dark current offset voltage and relative temperature coefficient effect corresponding thereto in the Red output voltage according to the present operating temperature and thereby provide a corrected Red output signal; a Green differential amplifier configured to receive the Green output voltage and the dark current offset voltage as inputs thereto and configured to use the dark current offset voltage to cancel the contribution of the dark current offset voltage and relative temperature coefficient effect corresponding thereto in the Green output voltage according to the present operating temperature and thereby provide a corrected Green output signal: and a Blue differential amplifier configured to receive the Blue output voltage and the dark current offset voltage as inputs thereto and configured to use the dark current offset voltage to cancel the contribution of the dark current offset voltage and relative temperature coefficient effect corresponding thereto in the Blue output voltage according to the present operating temperature and thereby provide a corrected Blue output signal; wherein each of the foregoing resistor components has a value ranging between 0.5 megaohms and 200 megaohms, each of the foregoing compensation capacitors has a value ranging between 2 picofarads and 400 picofarads, and the output signals of the Red, Green and Blue differential amplifiers represent the true intensities of the colors corresponding to the Red, Green and Blue output signals owing to increased temperature robustness provided by the transimpedance amplifiers.