1. A method implemented in a measuring instrument for detecting presence of at least one target, said method comprising: forming, by a first optical element of the measuring instrument, a field of view of an image sensor of the measuring instrument; creating relative movement between the first optical element of the measuring instrument and the image sensor of the measuring instrument causing motion of the field of view of the image sensor of said measuring instrument relative to said at least one target; capturing at least one digital image with said image sensor under motion of said field of view using an exposure time which is longer than an identifiable section of a regulating pattern for modulation of an optical radiation either emitted or reflected by said at least one target; and processing at least one portion of the at least one digital image for detecting in said at least one portion the identifiable section of the regulating pattern.