User manual LEICA DVM - 3D BROCHURE

[. . . ] One of the advantages of this method is that in addition to the height information, the texture of the specimen is also documented. Which influencing factors are determinative for successful creation of a 3-D surface variables influence lateral and vertical resolution? model and how do these 2 Optics and Surfaces Depth of field The author of the first publication on the subject of visually perceived depth of field was Max Berek, who published the results of his extensive experiments as early as 1927. Berek's formula gives practical values for visual depth of field and is therefore still used today. In simplified form, it is as follows: 1. Optics ­ in the balance between numerical aperture and depth of field In microscopy, depth of field is in many cases an empirically understood metric. [. . . ] This method is particularly well suited to textures that have a good contrast. As in many application areas of microscopy, the illumination is given an especially important status, as it frequently determines success or failure. Selecting a suitable illumination makes it possible to document even a specimen with little texture. For example, you can select an oblique incident illumination that makes even hidden structures visible. 4 Mechanics and Illumination 3. Mechanical resolution in the vertical direction The third influencing factor in this equation is the mechanical resolution in the vertical direction. This term means the smallest possible steps in the z-direction of the focusing drive, which is usually motorized. To make full use of the performance capacity of the optics, the smallest possible step must be smaller than the currently used depth of field, as otherwise image data are lost. A motorized focus drive with a resolution of 10m, for example, is suitable at a depth of field of 15m. Illumination Selecting the suitable illumination is critical to the success of the examination. The modular structure of the Leica DVM product concept enables you to combine the selected optics with the optimal illumination for the application. The following methods are available for selection: 1) Variable oblique incident illumination: This method changes the illumination direction from vertical to lateral. This approach is particularly suitable for visualizing scratches or small recesses. 2) Diffuser: For shiny surfaces, the dynamic range of the camera is insufficient in many cases and many areas of the specimen are overexposed. A diffuser provides reliable reduction of the overexposed area. 3) Coaxial illuminator: A coaxial illuminator is used for very shiny or reflective surfaces, such as wafers or metal sections. 4) Polarized light: is used to supress the reflections or for documentation of plastic materials. 5) Coaxial illuminator with directed light: In the applications described above, the directed light creates a three-dimensional impression of the specimen. This is helpful in many cases for determining the surface with greater accuracy. Which lateral and vertical resolutions are possible with a Leica DVM system?As described above, these parameters depend on various influencing factors, such as the surface structure or illuminator, and thus must be determined depending on the application. Interpolation attains a vertical resolution of one-half of the applied depth of field. [. . . ] For specimens with little texture, you can switch to another imaging method, such as confocal microscopy or interferometry. Leica DCM 3D, for example, combines both technologies in one instrument and is exceptionally well suited to specimens with little texture. The table on the left provides an overview of the performance capabilities and application areas of the Leica DVM systems. Here are the key optical and mechanical data of the equipment used: · Optics used: Leica VZ80 RC, 8:1 zoom with magnification range 50 ­ 400x, at a maximum magnification of 400x · Depth of field at maximum magnification of 400x is 80m · Resolution of the motorized focusing drive is 500 nm In the example provided here, a theoretical vertical resolution of 40m (depth of field / 2) is attained. The texture of the specimen to be examined has a high contrast range and can be distinguished easily by the software into sharp and out-of-focus areas. [. . . ]