The possibility that the UV filters transmitted a small fraction of long wavelength light sufficient to excite L cones was tested in a few experiments by adding a low-pass filter that transmitted only wavelengths longer than 450 nm.
This instrument has 488 nm and 635 nm lasers, and employs long pass, short pass, and bandwith filters that transmit wavelengths 530/30 nm (FL1), 585/42 nm (FL2), 670 nm (FL3), and 661/16 nm (FL4).
The intense blue fluorescence was only visible when viewed with emission filters that transmitted wavelengths from 413 nm to 483 nm.
The light source, utilized during the dark-light shifts, was a white lamp covered by a green filter (medium green filter 660, GamColor, Los Angeles, CA) that transmits light mainly in the 500 580 nm wavelength range.
This signal will then pass through a secondary filter that will estimate the originally transmitted signal.
Specifically, the impulse response of the equivalent filter that determines the effect on each output of the symbol sequence transmitted on each subcarrier, both with reference to AWGN and multipath channels, is obtained.
The authors of[1] propose a minimum mean square error (MMSE) filter that takes not only the subcarrier amplitudes but also their derivatives, to compute the transmitted symbol estimate.
Numerical validation illustrates the possibility to suppress interference without actually forming a spatial null in the direction towards interference, and the necessity to design transmit filters that are robust to uncertainties in the given scenario.
The third approach can be performed using an iterative procedure where we first filter the received signal with a bank of filters that is matched to the transmit FB.
This design includes diffraction grating and one-dimensional photonic crystals as band pass filters that reflect short light wavelengths and transmit longer wavelengths at the interface between two adjacent cells.
