Abstract: A method for detecting traces of material on a surface for forensic evidence gathering is disclosed. The surface is periodically illuminated with laser radiation. Pairs of images of the surface are recorded with one image in each pair recorded while the surface is illuminated and the other being recorded while the surface is not being illuminated. The images in each pair are subtracted and a video signal is generated from the subtracted images. The video signal can be displayed on a display device or recorded for later display and examination.

Abstract: Apparatus for circularizing an optical beam and directing the beam into an optical system has mutually perpendicular X, Y, and Z axes. The Z-axis is the propagation axis of the beam. A detector arrangement receives a sample of the optical beam. The detector arrangement has four detector elements arranged in four quadrants defined by an x-axis and a y-axis of the detector arrangement, perpendicular to each other. The x and y-axes of the quadrant detector are arranged at 45 degrees to the X and Y-axes of the apparatus. Signals from the four detector elements provide information on the extent to which the beam is not circular and on any displacement of the beam in the X and Y-axes.

Abstract: Apparatus for circularizing an optical beam and directing the beam into an optical system has mutually perpendicular X, Y, and Z axes. The Z-axis is the propagation axis of the beam. A detector arrangement receives a sample of the optical beam. The detector arrangement has four detector elements arranged in four quadrants defined by an x-axis and a y-axis of the detector arrangement, perpendicular to each other. The x and y-axes of the quadrant detector are arranged at 45 degrees to the X and Y-axes of the apparatus. Signals from the four detector elements provide information on the extent to which the beam is not circular and on any displacement of the beam in the X and Y-axes.

Abstract: Laser diode circuitry that controls the laser diode temperature as a function of laser diode current. Changes in the spectral output of the laser diode directly caused by adjustments to the operating current of the laser diode are offset by corresponding changes in the diode temperature. Diode temperature regulation circuitry automatically changes the diode temperature by monitoring the diode operating current. Alternately, when the diode current is adjusted to intentionally shift the spectral output of the diode, for example to maintain a frequency match to an external cavity resonance, the temperature regulation circuitry automatically changes the diode temperature to induce an additional spectral shift in the same direction, thereby inducing a current adjustment in the opposite direction that prevents large excursions in the amplitude of the operating current of the diode.