| 摘要 |
A plastic disk, 150 mm. dia., 2 mm. thick, has a central window, 40 mm. dia., with a 2 mm. rebate holding a polarised disk, 44 mm., 1 mm. thick. The central disk is so fitted that with the outer disk suspended freely from a hole near the rim, the plane of polarisation of the central disk is at 45 deg. to the vertical. Inclination to left or right, is marked for reference. Opt. a horizontal mounting base is established, giving the same result. With the vehicle perfectly horizontal, the central window is placed before the headlamp, whose beam, passing orthogonally through it, is monitored by e.g. a digital light meter. Headlamps are adjusted for minimum light received at the meter.
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