Photodetector having dark current correction
View Patent ↗A photodetector and method for making the same is disclosed. The photodetector includes a substrate having first, second, and third photodiodes and first and second pigment filter layers. The first, second, and third photodiodes generate first, second, and third photodiode output signals, respectively, each photodiode output signal being indicative of a light intensity incident on that photodiode and a dark current that is independent of the light intensity. The first and second pigment filter layers overlie the first and second photodiodes while a layer having both the first and second pigment filter layers overlie the third photodiode. An output circuit combines the first and third photodiode output signals to provide a first corrected output signal and combines the second and third photodiode output signals to provide a second corrected output signal.
1. A photodetector comprising:
a substrate having first, second, and third photodiodes that generate first, second, and third photodiode output signals, respectively, each photodiode output signal being indicative of a light intensity incident on that photodiode;
a first pigment filter layer overlying said first photodiode but not said second photodiode, said first pigment filter layer being transparent to light in a first band of wavelengths and opaque to light in a second band of wavelengths;
a second pigment filter layer overlying said second photodiode, but not said first photodiode, said second pigment filter layer being transparent to light in said second band of wavelengths and opaque to light in said first band of wavelengths;
a layer comprising said first and second pigment filter layers overlying said third photodiode; and
an output circuit that combines said first and third photodiode output signals to provide a first corrected output signal and that combines said second and third photodiode output signals to provide a second corrected output signal.
2. The photodetector of claim 1 wherein said output circuit subtracts a signal that is a multiple of said third photodiode output signal from said first and second photodiode output signals.
3. The photodetector of claim 1 wherein said first, second, and third photodiodes have areas that are integer multiples of the area of one of said photodiodes.
4. The photodetector of claim 1 further comprising a fourth photodiode and a third pigment filter layer overlying said fourth photodiode but not said first and second photodiodes, said fourth photodiode generating a fourth photodiode output signal indicative of a light intensity incident on said fourth photodiode and a dark current that is independent of that light intensity, wherein said output circuit further combines said third and fourth photodiode output signals to provide a third corrected output signal.
5. The photodetector of claim 4 wherein said third corrected output signal is corrected for said dark current.
6. The photodetector of claim 4 wherein said third pigment layer also overlies said third photodiode.
7. The photodetector of claim 1 wherein each of said photodiodes generates a dark current in the absence of light being received by said photodiodes and wherein said first and second output signals depend less on said dark current than said first and second photodiode output signals.