Evaluation of a commercially available laser-scanning microdensitometer for emission spectrographic measurements

It is shown that the LKB 2202 offers significant advantages over commercially available microdensitometric instruments developed specifically for evaluating spectrographic emulsions. Although limited primarily by the resolution provided by the HeNe laser source, this should not be a limiting factor in most applications. Increased resolution in the second dimension (for two-dimensional scans) is possible by changing from a cylindrical lens to a conventional spherical-surface lens. The LKB UltroScan XL Laser Densitometer, for example, offers a 100-μm spot beam in addition to the ellipsoidal scanning beam - this, however, will degrade the wavelength (x-axis) resolution attainable with the system. It should be possible to redesign the optics to obtain a scanning beam spot diameter of less than 10 μm, as the beam spot size should be limited only by diffraction. Additional modification of the stage holding the photographic emulsion would be required, though, if such a system's resolving capabilities were to be exploited fully.