Embodiments in accordance with the present invention provide an infinite impulse response filter circuit which can operate stably even when the coefficients are adaptively changed. A stage of an exposing head having a plurality of light source units provided thereon is supported by bases disposed at longitudinal direction opposite end portions thereof, and bases move in a sub-scanning direction which is the longitudinal direction of the stage when driven by a sub-scanning motor. Subjecting the same liquid monomer to the same test conditions then occurs in the absence of the soluble monomeric, oligomeric, or polymeric seed. In this case, through the use of at least two stacked crystal filters, it is possible to achieve an excellent out-of-band rejection also for \u201csingle-ended signals\u201d. The lubricious surface can be a fluoropolymer or a silicone surface, or other such reduced friction layer that has a reduced static coefficient of friction in comparison to standard powder coating finishes for retail shelving and other such retail display structures.