Optical filter array, photodetection device, and photodetection system
View Patent ↗An optical filter array is used in a photodetection device that generates image data separately for each of N (where N is an integer greater than or equal to 4) wavelength bands. The optical filter array includes a plurality of optical filters. The plurality of optical filters include plural types of optical filters differing in transmittance from each other in each of the N wavelength bands. Assuming that pi is an average of transmittances of the plurality of optical filters for light in an ith wavelength band (where i is an integer greater than or equal to 1 and less than or equal to N) of the N wavelength bands, a standard deviation of the average μ i of the transmittances for the N wavelength bands is less than or equal to 0.13.
1. An optical filter array that is used in a photodetection device generating image data separately for each of N wavelength bands, N being an integer greater than or equal to 4, the optical filter array comprising:
a plurality of optical filters, wherein
the plurality of optical filters include plural types of optical filters differing in transmittance from each other in each of the N wavelength bands,
assuming that μ i is an average of transmittances of the plurality of optical filters for light in an ith wavelength band of the N wavelength bands, i being an integer greater than or equal to 1 and less than or equal to N, a standard deviation σ μ of the average μ i of the transmittances for the N wavelength bands is expressed as
σ
μ
=
1
N
∑
i
=
1
N
(
μ
i
-
μ
μ
)
2
,
where
μ
μ
=
1
N
∑
i
=
1
N
μ
i
,
and
the standard deviation σ μ of the average si of the transmittances is less than or equal to 0.13.
2. The optical filter array according to claim 1 , wherein a transmittance of a peak in a histogram of the transmittances as obtained by measuring a transmittance of each of the plurality of optical filters for the light in the ith wavelength band with a photodetector that detects light intensity with a predetermined number of tones is smaller than the average μ i of the transmittances of the plurality of optical filters for the light in the ith wavelength band.
3. The optical filter array according to claim 1 , wherein at least one of the plurality of optical filters is a Fabry-Perot filter.
4. The optical filter array according to claim 1 , wherein
at least one of the plurality of filters includes a first reflective layer, a second reflective layer, and an intermediate layer between the first reflective layer and the second reflective layer, and
the at least one of the plurality of filters includes a resonant structure having a plurality of resonant modes differing in order from each other.
5. The optical filter array according to claim 1 , wherein a center wavelength λ i in the ith wavelength band and the average μ i of the transmittances of the plurality of optical filters for the light in the ith wavelength band have a positive correlation.
6. An optical filter array that is used in a photodetection device generating image data separately for each of N wavelength bands, N being an integer greater than or equal to 4, the optical filter array comprising:
a plurality of optical filters, wherein
the plurality of optical filters include plural types of optical filters differing in transmittance from each other in each of the N wavelength bands, and
assuming that σ i is a standard deviation of transmittances of the plurality of optical filters for light in an ith wavelength band of the N wavelength bands, i being an integer greater than or equal to 1 and less than or equal to N, an average of standard deviations σ i of the transmittances for the N wavelength bands is greater than or equal to 0.07.
7. An optical filter array that is used in a photodetection device generating image data separately for each of N wavelength bands, N being an integer greater than or equal to 4, the optical filter array comprising:
a plurality of optical filters, wherein
the plurality of optical filters include plural types of optical filters differing in transmittance from each other in each of the N wavelength bands, and
assuming that μ i is an average of transmittances of the plurality of optical filters for light in an ith wavelength band of the N wavelength bands, i being an integer greater than or equal to 1 and less than or equal to N, that σ i is a standard deviation of the transmittances of the plurality of optical filters for the light in the ith wavelength band, and that R i =(μ i +3σ i )/(μ i −3σ i ), an average of R i for the N wavelength bands is greater than or equal to 2.0.
8. A photodetection device comprising:
the optical filter array according to claim 1 ; and
an image sensor that detects light having passed through the optical filter array.
9. A photodetection system comprising:
the photodetection device according to claim 8 ; and
a signal processing circuit that generates image data for each of the N wavelength bands in accordance with a signal outputted from the image sensor.