Photo detector with compensated output and method involving same

A photo sensor with compensation comprising:

• a photo cell for providing a first signal indicative of a light level;
• an environmental sensor configured to provide a second signal indicative of an environmental parameter;
• and
• a processor responsive to the first signal and the second signal and configured to provide a compensated signal that is indicative of an absolute light level;
• wherein the processor is further configured to calculate the compensated signal based the first signal and the second signal and wherein the processor adjusts the first signal to account for a sensitivity of the photo cell relative to temperature to provide the compensated signal, the temperature indicated by the second signal,
• wherein the processor adjust the first signal in accordance with one or more temperature coefficients associated with a function relating the first signal to the temperature when the light level is constant to provide a temperature compensated signal, and
• wherein the processor adjusts the temperature compensated signal in accordance with a light calibration coefficient to provide the compensated signal that is indicative of the absolute light level.

A method of determining parameters for compensation of a photo sensor, the method comprising:

• varying an input light level to the photo sensor while controlling a temperature of the photo sensor to provide first indications of the light level with each of the first indications corresponding to a respective one of a plurality of light levels;
• determining one or more light calibration coefficients based on the first indications of the light level;
• varying the temperature of the photo sensor while controlling the input light level to provide second indications of the light level with each of the second indications corresponding to a respective one of a plurality of temperatures;
• and
• determining one or more temperature coefficients based on the second indications of the light level, wherein the light calibration coefficients and the temperature coefficients are suitable for use in converting a light level indication from the photo sensor to a compensated signal indicative of an absolute light level.

A method of compensating an output of a photo sensor to provide a calibrated light reading comprising:

• obtaining one or more light calibration coefficients and one or more temperature coefficients corresponding to the photo sensor;
• getting a light output indication for the photo sensor and a temperature indication from a temperature sensor;
• and
• calculating the calibrated light reading based on the one or more temperature coefficients, the one or more light calibration coefficients, the temperature indication, and the light output indication, the calibrated light reading indicative of an absolute light level.

A method of compensating a photo sensor comprising;

• providing a first signal indicative of a light level;
• providing a second signal indicative of an environmental parameter;
• and
• calculating, responsive to the first signal and the second signal, a compensated signal that is indicative of an absolute light level;
• where calculating the compensated signal is based the first signal and the second signal and comprises adjusting the first signal to account for a sensitivity of a photo cell relative to the light level to provide the compensated signal, and
• wherein adjusting the first signal comprises adjusting the first signal in accordance with a light calibration coefficient and a calibration constant associated respectively with the slope and intercept of a line relating the first signal and the light level when the second signal is constant.

A method of compensating a photo sensor comprising:

• providing a first signal indicative of a light level;
• providing a second signal indicative of an environmental parameter;
• and
• calculating, responsive to the first signal and the second signal, a compensated signal that is indicative of an absolute light level;
• wherein calculating the compensated signal is based the first signal and the second signal and comprises adjusting the first signal to account for a sensitivity of a photo cell relative to the light level to provide the compensated signal,
• wherein adjusting the first signal comprises adjusting the first signal in accordance with one or more temperature coefficients associated with a function relating the first signal to the temperature when the light level is constant to provide a temperature compensated signal,.
• wherein adjusting the first signal comprises adjusting the temperature compensated signal in accordance with a light calibration coefficient to provide the compensated signal that is indicative of the absolute light level.