Collimation of laser beam plays a very important role in many aspects of applied optics including human eye aberration
measurement. In this article, a new type of method which could be used to collimate laser beam is proposed. This new
method of adjustment is characterized by objective, measurable and repeatable. On the other hand, we have also
established a complete ocular aberration measurement system which is based on the principle of Hartmann-Shack and
used Hartmann-Shack wavefront sensor as its detector. In every stage of installation of this ocular aberration system, the
degree of defocus and collimation is measured and adjusted in accordingly. Hence, the effective focal length of each
length we use is precisely measured and the collimation of laser beam is reassured. Our experiments clearly show that
this kind of new ocular aberration measurement system can effectively compensate the errors of lens and installation
deviation during the process of establishing ocular aberration measuring system. Considering this technique could be
used in other fields of area where highly calibrated parallel light beams are needed, this improvement could be very
crucial for the use of future.
The impact on the measurement accuracy caused by uncollimated illumination beam during the process of human eye
aberration measurement by using Hartmann-Shack wavefront sensor has been studied. The principle of Hartmann-Shack
wavefront sensor has been introduced. The diopter curve corresponding to the installation errors of lens has been
calculated. And the according curve reveals that the diopter of illumination beam at the section of entrance pupil is quite
sensitive to the installation errors of lens. The impact on wavefront at the exit pupil under the illumination of
uncollimated beam has been analyzed and relative experiments have been done. The experiments show seldom impact of
it. Quantitative relationship between the precision of ocular aberration measurement and installation errors of lens is
proposed. Experiments to quantitatively simulate the installation errors have been done. The experimental results are in
accordance with the theoretical analysis we made and the collimation of illumination beam has an obvious and direct
influence on the measurement precision of ocular aberration.
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