shown the photodetector 10 is positioned on the x y stage 19 directional actuators 22 and 23 may be used to drive the x y stage 19 in x direction a direction indicated by an arrow 24 and y direction a direction indicated by an arrow 25 respectively the directional actuators 22 and 23 may comprise direct acting actuators such as a piezoelectric device or a stepping motor as shown in fig1 the directional actuators 22 and 23 are controlled by a signal from a personal computer 16 in an alternate embodiment a manually controlled adjustment mechanism 19 is contemplated those skilled in the art will appreciate the present invention is greatly different from the prior art systems in that the diffraction device 18 which is positionable within the propagation path of the laser light 2 is capable of adjusting the optical axis in the optical path between the light source 1 and the photodetector 10 in addition further adjustments to the optical axis may be achieved with the adjusting mechanism 19 coupled to the photodetector 10 fig2 shows a second embodiment of the present invention in which a mirror 26 in communication with an optical axis adjusting mechanism 27 is provided the mirror 26 directs the laser light 2 emitted from the light source 1 at a 90 degree angle into the beam expander 6 as shown the optical axis adjusting mechanism 27 which is controlled by the cpu 15 is capable of moving the mirror 26 in the directions indicated by the arrows 28 and or 29 fig3 shows a third embodiment of the present invention in which an optical axis adjusting mechanism 30 which is controllable by the cpu 15 is provided as shown in fig3 the optical axis adjusting mechanism 30 is capable.