Filter array with reduced stray focused light
An apparatus is disclosed comprising an optical filter array including an array of optical filter elements; wherein each optical filter element has opposing mutually parallel principal faces connected by sidewalls including at least one pair of opposing trapezoidal sidewalls and at least one pair of opposing sidewalls that are not mutually parallel; and wherein the opposing mutually parallel principal faces of the filter elements collectively define optical entrance and exit apertures of the optical filter array and include interference filters. Further disclosed is a method of illuminating such a filter array.
1. An apparatus comprising:
an optical filter array comprising an array of optical filter elements which includes an array of interior optical filter elements which are not the outermost optical filter elements of the optical filter array;
wherein each optical filter element has opposing mutually parallel principal faces connected by two pairs of opposing trapezoidal sidewalls in which the opposing trapezoidal sidewalls of each pair are not mutually parallel, and the opposing mutually parallel principal faces of each interior optical filter element include larger and smaller opposing mutually parallel principal faces connected by the two pairs of opposing trapezoidal sidewalls; and
wherein the larger principal faces of the interior optical filter elements collectively define a diverging optical aperture of the optical filter array and the smaller principal faces of the interior optical filter elements collectively define a converging optical aperture of the optical filter array.
2. The apparatus of claim 1 further comprising:
an optical system configured to generate converging or diverging light wherein at least one pair of opposing sidewalls of each filter element is aligned with a local angle of the converging or diverging light.
3. The apparatus of claim 1 wherein the optical filter elements comprise:
a plurality of optical filter elements of different optical filter types defined by different interference filters.
4. The apparatus of claim 1 wherein the interference filters of the optical filter elements comprise pass-band filters or notch filters.
5. A method comprising:
providing an optical filter array comprising an array of optical filter elements wherein each optical filter element has opposing mutually parallel principal faces connected by sidewalls including two pairs of opposing trapezoidal sidewalls in which the opposing trapezoidal sidewalls of each pair are not mutually parallel, and wherein the opposing mutually parallel principal faces of each interior optical filter element include larger and smaller opposing mutually parallel principal faces connected by the two pairs of opposing trapezoidal sidewalls, and wherein the opposing mutually parallel principal faces of the filter elements include interference filters; and
illuminating the optical filter array with converging or diverging light having local angle comporting with sidewall angles of the sidewalls of the filter elements.
6. The apparatus of claim 1 further comprising:
an optical system generating converging light that enters the optical filter array at the diverging optical aperture and exits the optical filter array at the converging optical aperture.
7. The apparatus of claim 1 further comprising:
an optical system generating diverging light that enters the optical filter array at the converging optical aperture and exits the optical filter array at the diverging optical aperture.
8. The apparatus of claim 1 wherein adjacent optical filter elements of the optical filter array are secured together at joining trapezoidal sidewalls.