Light sensor arrangement and method for temperature compensation in a light sensor arrangement
A light sensor arrangement according to the proposed principle comprises at least one first unshielded well (D 0 ) and at least one second shielded well (D 1 ) in a substrate (P). The at least one first unshielded well (D 0 ) is being exposed to incident light (λ) and configured to generate a first sensor signal (Ch 0 ) as a function of the incident light (λ). The at least one second shielded well (D 1 ) in the substrate (p) being shielded from the incident light (λ) and configured to generate a second sensor signal (Ch 1 ) as a function of the incident light (λ). The light sensor arrangement further comprises means for temperature compensation providing the first and second sensor signals (Ch 0 , Ch 1 ) as temperature compensated sensor signals as a function of substrate temperature. Means to determine spectral content of the incident light (λ) are provided to determine the spectral content as a function of the temperature compensated first and second sensor signals (Ch 0 , Ch 1 ).
1. A light sensor arrangement comprising:
at least one first unshielded well in a substrate being exposed to incident light and configured to generate a first sensor signal as a function of the incident light;
at least one second shielded well in the substrate being shielded from the incident light and configured to generate a second sensor signal as a function of the incident light;
a temperature sensor for temperature compensation, the temperature sensor configured to provide the first and second sensor signals as temperature compensated sensor signals as a function of substrate temperature; and
a processing unit configured to determine spectral content of the incident light as a function of the temperature compensated first and second sensor signals,
wherein the at least one first unshielded well, the at least one second shielded well and the temperature sensor are embedded in the substrate, and
wherein the at least one first unshielded well and the at least one second shielded well correspond to photodiodes, the photodiodes being respectively formed by the least one first unshielded well and the at least one second shielded well.
2. The light sensor arrangement according to claim 1 , wherein the temperature sensor is configured to generate a temperature signal depending on the substrate temperature.
3. The light sensor arrangement according to claim 2 , wherein the temperature sensor comprises a temperature diode comprising a third well in the substrate.
4. The light sensor arrangement according to claim 3 , wherein the third well is of the same type as the at least one first unshielded well and the at least one second shielded well in the substrate.
5. The light sensor arrangement according to claim 3 , wherein the at least one first unshielded well, the at least one second shielded well, and the third well comprise an n-type semiconductor, and
wherein the substrate comprises a p-type semiconductor.
6. The light sensor arrangement according to one of claims 2 to 4 ,
wherein a memory is connected to the processing unit and configured to store pre-determined calibration data referenced as a function of a reference temperature,
wherein the processing unit is coupled to the temperature sensor and to the at least one first unshielded well and the at least one second shielded well via the substrate, respectively, to receive the temperature signal as well as the first and second sensor signal,
wherein the processing unit comprises is configured to determine a signal ratio of the first and second sensor signal,
wherein the processing unit comprises is configured to select calibration data from the memory as a function of the signal ratio and the reference temperature, and
wherein the processing unit comprises is configured to provide a temperature compensated signal ratio and the temperature compensated first and second sensor signal based on the selected calibration data.
7. The light sensor arrangement according to claim 6 , wherein the substrate is coupled to the processing unit via an analog-to-digital-converter,
wherein the processing unit comprises a digital signal processor, and
wherein the memory comprises a digital memory.
8. The light sensor arrangement according to claim 6 , wherein the memory comprises a table of calibration data or a calibration formula to generate the calibration data, and
wherein the table and formula are readable by the processing unit.
9. The light sensor arrangement according to claim 6 , further comprising a calculation unit:
connected to the processing unit to receive the temperature compensated signal ratio and the temperature compensated first and second sensor signal, and
configured to determine from the temperature compensated signal ratio and as a function of the temperature compensated first and second sensor signal a type of light source emitting the incident light and/or a lux value of the incident light.
10. The light sensor arrangement according to claim 1 , wherein the temperature compensation is further provided by at least one component within the substrate.
11. The light sensor arrangement according to claim 10 , wherein the at least one component is positioned proximate to the at least one first unshielded well and the at least one second unshielded well in the substrate.
12. The light sensor arrangement according to claim 11 , wherein the at least one component is configured to sense photodiode junction temperature corresponding to the first and second sensor signals.
13. The light sensor arrangement according to claim 1 , wherein the temperature compensation is wavelength dependent, and wherein the sensor signals are wavelength dependent such that spectral content can be extracted from them.
14. A method for temperature compensation in a light sensor arrangement comprising the steps of:
acquiring a first sensor signal by at least one first unshielded well in a substrate being exposed to incident light;
acquiring a second sensor signal by at least one second shielded well in the substrate being shielded from the incident light;
providing, by a temperature sensor, the first and second sensor signal as temperature compensated first and second sensor signals as a function of substrate temperature; and
determining a spectral content of the incident light as a function of the temperature compensated first and second sensor signals,
wherein the at least one first unshielded well, the at least one second shielded well and the temperature sensor are embedded in the substrate, and
wherein the at least one first unshielded well and the at least one second shielded well correspond to photodiodes, the photodiodes being respectively formed by the least one first unshielded well and the at least one second shielded well.
15. The method according to claim 14 , wherein the substrate temperature is determined:
in parallel to acquiring the first and second sensor signal or
during a temperature measurement mode of operation alternating with the acquisition of the first and second sensor signal.
16. The method according to claim 14 or 15 , further comprising the steps of:
calculating a signal ratio from the first and second sensor signal as acquired by the at least one first unshielded well and the at least one second shielded well corresponding to the photodiodes;
selecting calibration data from a pre-determined table and/or formula, referenced as a function of the signal ratio and of a reference temperature, depending on the signal ratio and substrate temperature; and
providing a temperature compensated signal ratio and the temperature compensated first and second sensor signal based on the selected calibration data.
17. The method according to claim 14 , further comprising determining from the temperature compensated signal ratio a type of light source emitting the incident light, or determining from the temperature compensated signal ratio and as a function of the temperature compensated first and second sensor signal a lux value of the incident light.
18. The method according to claim 14 , further comprising the step of determining the type of light source emitting the incident light as further function of the second sensor signal of the at least one second shielded well.
19. A light sensor arrangement comprising:
at least one first unshielded well in a substrate being exposed to incident light and configured to generate a first sensor signal as a function of the incident light;
at least one second shielded well in the substrate being shielded from the incident light and configured to generate a second sensor signal as a function of the incident light;
a temperature sensor configured to provide the first and second sensor signals as temperature compensated sensor signals as a function of substrate temperature,
wherein the substrate has a depth adjusted to the absorption distance of the incident light in the substrate material, and is chosen to be larger than the absorption distance at a pre-determined wavelength of the incident light and at a pre-determined substrate temperature; and
a processing unit configured to determine spectral content of the incident light as a function of the temperature compensated first and second sensor signals,
wherein the at least one first unshielded well, the at least one second shielded well and the temperature sensor are embedded in the substrate, and
wherein the at least one first unshielded well and the at least one second shielded well correspond to photodiodes, the photodiodes being respectively formed by the least one first unshielded well and the at least one second shielded well.