| 摘要 |
<p>The beam is scanned in a first direction over a range of scan angles from -32[deg] to +32[deg] and the lens assembly is configured to produce an achromatic focussed beam spot in the wavelength range of 670 to 780 nanometers. The recording medium and the focussed spot are translated relative to each other to scan in a direction perpendicular to the first direction to produce a two dimensional image. The recording medium and the focussed spot are translated relative to each other to scan in a direction perpendicular to the first direction to produce a two dimensional image. The medium may be an electrostatic recording device or a photosensitive film, plate or paper. The lens assembly may be an f-theta assembly with a first lens with a negative power and a refractive index in the range 1.64 to 1.85, and two further lenses with positive powers and refractive indices in the ranges 1.6 to 1.75 and 1.65 to 1.75. An independent claim is included for an f-theta lens assembly.</p> |
