Image acquisition technique for high dynamic range scenes using a multiband camera

Multispectral Filter-Wheel Cameras: Geometric Distortion Model and Compensation Algorithms

“…As our results in Section IV confirm, CA can be captured well by an affine transformation matrix (18) This model remains valid when, without loss of generality, the effect of chromatic aberration is assumed to be located at the position , i.e., at the projection center. Taking into account CA, the distortion model (17) becomes (19) where mathematically precedes because the lens (causing chromatic aberration) precedes the optical bandpass filter. Amongst others, adds elements on the secondary diagonal to the transformation matrix, which were equal to zero in (17).…”

“…Demosaicking is circumvented by applying a piezo-driven pixel shift to the sensor, which ensures that each color component is sampled by the complete sensor matrix. In [18] and [19], this RGB-based concept is improved further by using two 3CCD HDTV cameras with a similar customized spectral filter as described above. The camera pair is able to record multispectral videos and does not exhibit moving mechanical components.…”

“…Interestingly, a related principle called the "6-Primary Display" [20]- [22] exists, which employs two RGB projectors with additional appropriate spectral filters to project images with higher color fidelity. To enable acquisition with a higher dynamic range, a neutral density filter is also attached to one 3CCD camera [19]. Another possibility to avoid mechanical parts is the application of a liquid crystal tunable filter (LCTF) [23], whose filter characteristics can be adjusted by applying different voltages.…”

Multispectral high dynamic range imaging

“…Because typical reflectance spectra are smooth, it is sufficient and common 3,9,12 to use sampled spectra, e.g., with a number of N = 61 spectral samples, which cover a wavelength range from λ 1 = 400nm to λ N = 700nm. Towards this end, we write Eq.…”

“…The outcome of this is that three passband halves are acquired with full sensitivity, while the other ones are acquired with a reduced sensitivity due to the neutral density filter. Therefore, the innovative concept in [9] offers only the limited number of two exposure levels, which may not suffice for many HDR applications. Another limitation occurs when one half of a passband is saturated: In this case, there is no estimation for that specific wavelength range at all, since the passband halves are shared by both cameras.…”