The lensometers is also called measural lens dioptre instrument, to measure spherical lens dioptre, cylindric lens dioptre and axis, prism dioptre, and lens optical center etc.
Since off-axis wander results in images which have astigmatism when the prism is placed in a converging beam, Glan types have slightly better imaging qualities than Nicla types.
因为当棱镜置于会聚光束中时，离轴漂移造成有像散的像，格兰型棱镜的成像质量比尼·科尔型略好。
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In this paper, according to the law of prism turning, due to the errors in planar reflector assembling, light axis departure from systemic axis and light turning are analyzed.