Calculating Global Overlap Windows in Sequential Row Readout Image Sensors
Calculate global overlap by subtracting array readout time from total exposure; fire external illumination within this window to emulate global shuttering.
Bandpass Interference Filter
Spectral Boundary
Optical components designed to transmit a specific range of wavelengths while rejecting all others through constructive and destructive wave interaction provide precise control over light paths. A bandpass interference filter uses thin layers of dielectric materials deposited onto a glass substrate to create this selectivity. These coatings are calculated to an exact thickness to ensure that only the target band remains at the output side.
Transmission Characteristic
Peak transmittance usually occurs at the center of the passband and decreases as the edge of the wavelength range approaches. This efficiency depends on the quality of the vacuum deposition process and the refractive index of the materials used. Moisture absorption or temperature shifts can cause the center wavelength to drift away from its calibrated point.
Rejection Capacity
Blocking performance outside the desired band is defined by the optical density which determines how much stray light reaches the sensor. High rejection levels prevent thermal noise or ambient light from polluting the measurement signal. Angle of incidence affects performance because a tilt in the bandpass interference filter causes the passband to shift toward shorter wavelengths.
Installation Stability
Mechanical mounting must account for thermal expansion to avoid stressing the delicate coating layers. Mechanical stress leads to delamination or spectral shifts that invalidate the initial calibration. Hard coatings provide better environmental durability than soft films.