The imaging properties of parametric infrared up-converters

Self-radiant or illuminated infrared objects can be made visible by an image unconverter--a device in which the infrared interacts parametrically with an optically nonlinear material with a strong laser pump beam (1--3). We will discuss the three-dimensional nature, resolution, location, magnification and aberrations of images produced by such a device. These properties have been demonstrated in the laboratory. A 16 mm film transparency was illuminated by the output of continuously-pumped, repetitively Q-switched Nd:YAG laser. The light scattered by this object was mixed within a 1.2 cm cube of KDP with a 1.064 micron pump beam derived from the same laser. The 5320 Å upconverted object is clearly visible to the eye. Photographs of it have a resolution of 300 × 200 lines and 850 object line-pairs per inch, which is comparable with the infrared image.