An optical element holder (120, 220, 320, 420, 520, 620, 720) for an optical instrument, the optical element holder comprising: a body comprising an optical input side, an optical output side, a thickness along a longitudinal axis between the optical input side and the optical output side, and a plurality of receptacles (256, 356, 456, 556, 656, 756) configured to retain respective optical elements and generally arranged in a transverse plane orthogonal to the longitudinal axis, wherein each receptacle is open to the optical input side and to the optical output side to define an optical path through the body parallel to the longitudinal axis; and a plurality of pusher components (374, 474, 574) extending from the body, each pusher component comprising a spring member (380, 480, 580) and at least one contact surface (378, 478, 578) positioned to be biased by the spring member toward at least one of the receptacles (256.. 756) and into contact with an optical element retained in the receptacle, wherein each pusher component (374, 474, 574) is configured to apply a biasing force against at least one optical element retained in a respective one of the receptacles (256.. 756) to retain the at least one optical element in an aligned position at which the at least one optical element is parallel to the transverse plane, wherein the body comprises a plurality of receptacle surfaces, each receptacle (256.. 756) is defined by at least one of the receptacle surfaces, and each pusher component (374, 474, 574) is configured to apply the biasing force such that the at least one optical element in the aligned position is biased into contact with at least one of the receptacle surfaces, wherein the spring member (380, 480, 580) is a planar structure comprising an elongated dimension and is deflectable in a direction generally orthogonal to the elongated dimension, and wherein each pusher component (374, 474, 574) comprises a contact element extending from or separate from the spring member (380, 480, 580), and the contact element comprises the contact surface (378, 478, 578, characterized in that each optical element receptacle (256, 356, 456, 556, 656, 756) includes a radial opening (236, 336, 436, 536, 636, 736) adapted for loading the optical element into the optical element receptacle via the radial opening along a radial direction. a body comprising an optical input side, an optical output side, a thickness along a longitudinal axis between the optical input side and the optical output side, and a plurality of receptacles (256, 356, 456, 556, 656, 756) configured to retain respective optical elements and generally arranged in a transverse plane orthogonal to the longitudinal axis, wherein each receptacle is open to the optical input side and to the optical output side to define an optical path through the body parallel to the longitudinal axis; and a plurality of pusher components (374, 474, 574) extending from the body, each pusher component comprising a spring member (380, 480, 580) and at least one contact surface (378, 478, 578) positioned to be biased by the spring member toward at least one of the receptacles (256.. 756) and into contact with an optical element retained in the receptacle, wherein each pusher component (374, 474, 574) is configured to apply a biasing force against at least one optical element retained in a respective one of the receptacles (256.. 756) to retain the at least one optical element in an aligned position at which the at least one optical element is parallel to the transverse plane, wherein the body comprises a plurality of receptacle surfaces, each receptacle (256.. 756) is defined by at least one of the receptacle surfaces, and each pusher component (374, 474, 574) is configured to apply the biasing force such that the at least one optical element in the aligned position is biased into contact with at least one of the receptacle surfaces, wherein the spring member (380, 480, 580) is a planar structure comprising an elongated dimension and is deflectable in a direction generally orthogonal to the elongated dimension, and wherein each pusher component (374, 474, 574) comprises a contact element extending from or separate from the spring member (380, 480, 580), and the contact element comprises the contact surface (378, 478, 578, characterized in that each optical element receptacle (256, 356, 456, 556, 656, 756) includes a radial opening (236, 336, 436, 536, 636, 736) adapted for loading the optical element into the optical element receptacle via the radial opening along a radial direction.