the optical image the objective lenses 32 a and 32 b may be composite objective lenses the laser 12 emits a light beam that is collimated by the collimator lens 14 and incident on the beam splitter 16 the transmitted part of the beam is captured by the forward sense photodetector 18 for measuring the light output of the laser 12 the results of this measurement are used by a laser driver not shown to control the output of the laser 12 the reflected part of the light beam is incident on the spot generator 20 the spot generator 20 modulates the incident light beam to produce an array of light spots in a sample placed in the sample layer 26 the imaging optics 32 generates on the pixelated photodetector 34 an optical image of the sample layer 26 illuminated by the array of scanning spots the captured images are processed by the video processing ic 36 to a digital image that is displayed and possibly further processed by the pc 38 in view of cost the photodetector 34 is preferably an off the shelf image sensor advantageously the total bandwidth of the image sensor 34 is utilized if the method of windowing is applied in this method part of the rows and or columns are shut down so that only the pixels within the u201c window u201d are read out this gives an increase in frame rate and thus in throughput equal to the ratio of the total sensor area and the window area referring to fig2 there is.