The most utilized laser scanners, galvanometer-based or with polygonal mirrors produce non-linear scanning. This is a major issue of these devices, as for most applications a constant scan speed (therefore a linear scanning) should be provided. While common linearizing solutions include for example expensive F-theta lenses, we study a simple, lowcost solution, with a two-mirror angular device – in order to linearize the scanning function by increasing the distance between the scanner and its objective lens (i.e., by using an objective lens with an as high as possible object focal length) in a compact solution. By using supplemental mirrors, this object focal length can be folded in order to minimize the dimensions of the assembly. We have used in a previous study a classical approach to this problem. In the present one we propose another method to solve the problem of the total number of images produced by the two-mirror device, as well as the maximum scanner-to-lens distance that can be introduced by the device. The impact of the constructive parameters of the device on these characteristics is pointed out. Design conclusions can be drawn from this study.
Most laser scanners applications require a linear scanning function, i.e., a constant scanning speed. One of the possible
and simplest methods to achieve this – for both scanners with rotational (i.e., polygonal) or oscillatory (i.e.,
galvanometer) mirrors – is to increase the distance between the mirror and the scanned plane. In order to achieve this, we
propose and study a simple and low-cost optical configuration with two plane mirrors set at a certain adjustable angle.
The multiple reflections of a laser beam on the two mirrors are considered, the number of images produced is deduced,
and the total optical path is obtained. The device is considered for a dimensional measurement application, usually called
an optical micrometer - in a set-up which includes the two angular mirrors between a laser scanner with oscillatory or
rotational mirrors and its objective lens. This simple device increases the path of the laser beam between the scanning
mirror and the lens in a compact construct. The linearity of the scanning function is thus increased, while the total size of
the system is reduced – with regard to other possible set-ups. A multi-parameter analysis is proposed and briefly pointed
out with regard to the characteristics of the system.
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