Optical sensor and method for detecting electromagnetic radiation
An optical sensor comprises at least four detection channels, where each detection channel comprises a photodetector and a filter with a respective transmission spectrum. The transmission spectra of the at least four filters are different from one another, and the transmission spectra are set such that each of the three CIE color matching functions is a linear combination of the transmission spectra of at least two of the filters. Furthermore, a method for detecting electromagnetic radiation is provided.
1. An optical sensor operable for color measurement and spectrum reconstruction, the optical sensor comprising:
at least four detection channels, where each detection channel comprises a photodetector and a filter with a respective transmission spectrum, wherein:
the transmission spectra of the at least four filters are different from one another,
the transmission spectra are set such that each of the three CIE color matching functions is identical to a linear combination of the transmission spectra of at least two of the filters, and
the transmission spectra partially overlap with each other and are distributed over the whole visible range of the electromagnetic spectrum.
2. The optical sensor according to claim 1 , wherein each transmission spectrum is assigned a scaling factor for at least one linear combination yielding one of the CIE color matching functions.
3. The optical sensor according to claim 1 , wherein the wavelength of maximum transmission is at least 380 nm and at most 780 nm for each filter.
4. The optical sensor according to claim 1 , wherein the wavelengths of maximum transmission of the filters are equally spaced from each other.
5. The optical sensor according to claim 4 , wherein the transmission spectra of the filters are linearly independent.
6. The optical sensor according to claim 1 , wherein the transmission spectra are set such that at least one transmission spectrum is employed for the linear combinations of two CIE color matching functions.
7. The optical sensor according to claim 1 , wherein the filters are one of the following:
interference filters,
absorption filters,
plasmonic filters.
8. The optical sensor according to claim 1 , wherein the filters are a combination of at least two of the following:
interference filters,
absorption filters,
plasmonic filters.
9. A method for detecting electromagnetic radiation, the method comprising:
providing an optical sensor which comprises at least four detection channels, where each detection channel comprises a photodetector,
providing a filter with a transmission spectrum for each detection channel, where the transmission spectra of the at least four filters are different from one another, partially overlap each other, and are distributed over the whole visible range of the electromagnetic spectrum, such that each of the three CIE color matching functions is identical to a linear combination of the transmission spectra of at least two of the filters,
detecting electromagnetic radiation to be emitted from a light source with the optical sensor, where each detection channel detects a fraction of the electromagnetic radiation in a range of wavelengths that is within the transmission spectrum of the respective filter and where each detection channel provides a channel signal,
determining from the channel signals a tristimulus value of the electromagnetic radiation, and
reconstructing by means of suitable mathematical algorithms and/or matrix interpolation operations from the channel signals the spectrum of the electromagnetic radiation.
10. The method according to claim 9 , wherein each transmission spectrum is assigned a scaling factor for at least one linear combination yielding one of the CIE color matching functions.
11. The method according to claim 10 , wherein at least two channel signals are multiplied with the respective scaling factors of the transmission spectra of the filters of the respective detection channels and added to give a tristimulus value.
12. The method according to claim 9 , wherein the linear combination of the transmission spectra of at least two of the filters is the sum of at least two transmission spectra that are multiplied with their respective scaling factors.
13. The method according to claim 9 , wherein the channel signal of each detection channel comprises the intensity of electromagnetic radiation detected by the respective detection channel.
14. The method according to claim 9 , wherein at least one channel signal is employed for determining two tristimulus values.
15. The method according to claim 9 , wherein a color measurement is provided which is based on the CIE color matching functions.
16. The method according to claim 9 , wherein the three tristimulus values are determined.
17. The method according to claim 9 , wherein the wavelength of maximum transmission of at least one transmission spectrum is equal to the wavelength of maximum sensitivity of one of the CIE color matching functions.
18. The method according to claim 9 , wherein at least two channel signals are employed for reconstructing the spectrum of the detected electromagnetic radiation.
19. The method according to claim 9 , further comprising determining a remission, wherein determining the remission comprises
reconstructing from at least two channel signals the spectral composition of the detected electromagnetic radiation; and
determining from the spectral composition the color impression of the light source.