Optical bandpass filters play a decisive role in multispectral imaging. Various multispectral cameras use this
type of color filter for the sequential acquisition of different spectral bands. Practically unavoidable, small tilt
angles of the filters with respect to the optical axis influence the imaging process: First, by tilting the filter,
the center wavelength of the filter is shifted, causing color variations. Second, due to refractions of the filter,
the image is distorted geometrically depending on the tilt angle. Third, reflections between sensor and filter
glass may cause ghosting, i.e., a weak and shifted copy of the image, which also depends on the filter angle. A
method to measure the filter position parameters from multispectral color components is thus highly desirable.
We propose a method to determine the angle and position of an optical filter brought into the optical path
in, e.g., filter-wheel multispectral cameras, with respect to the camera coordinate system. We determine the
position and angle of the filter by presenting a calibration chart to the camera, which is always partly reflected
by the highly reflective optical bandpass filter. The extrinsic parameters of the original and mirrored chart can
then be estimated. We derive the angle and position of the filter from the coordinates of the charts. We compare
the results of the angle measurements to a ground truth obtained from the settings of a high-precision rotation
table and thus validate our measurement method. Furthermore, we simulate the refraction effect of the optical
filter and show that the results match quite well with the reality, thus also confirming our method.