| 摘要 |
A laser scanner having first and second scanning mirrors and a correction circuit that removes distortions caused by interaction between the scanning mirrors. Preferably, the first scanner mirror is an off-axis mirror that is positioned to produce a single, substantially invariant pupil on the second scanning mirror. Preferably the scanner uses a reflective beam expander to magnify an input laser beam received from a laser source. Preferably, the reflective beam expander is implemented using two spherical mirrors positioned to form the input laser beam into a Z-folded beam path. The folded beam path increases the distance between the laser source and the focusing lens, which results in a clear focused spot and does so using spherical mirrors which are much less expensive than the infrared lenses used in the prior art. The reflective beam expander is also wavelength insensitive. In one embodiment, the correction circuit employs analog elements to implement a quadratic approximation of the geometric distortions caused by interaction of the scanning axes. In another embodiment, the correction circuit employs programmable logic devices to create corrected mirror control signals based on correction values stored in digital memory units. |
