Resolution with mirror lenses

As already mentioned, resolution with mirror lenses can be improved by operating at shorter wavelengths, the only difficulty is to find resist/lamp combinations that give short enough exposure times. Several resists have already been found that are satisfactory for 300 nm exposure and there are a number of others with potential for operation at 250 nm (11). The major difficulty with deep UV resists is not sensitivity but the need to find resins that are transparent enough to allow uniform exposure to the bottom of the resist. 

The first resolution was, of course, the one Pasteur carried out with his hand lens and tweezers (Sec. 4.6). But this method can almost never be used, since racemic modifications seldom form mixtures of crystals recognizable as mirror images. Indeed, even sodium ammonium tartrate does not, unless it crystallizes at a temperature below 28 . Thus partial credit for Pasteur s discovery has been given to the cool Parisian climate— and, of course, to the availability of tartaric acid from the winemakers of France. 

In either the LCD or micromirror dynamic mask, the LCD or micromirror array consists of a large number of individually controllable pixels. For example, current micromirror arrays that contain more than 800,000 individually addressable mirrors are available where each mirror in the array is a square mirror that is roughly 15 p long on each side. Therefore, again using lens-based projection optical systems, it is possible to produce complex 3D objects with feature resolution down in the micron scale range and below quite easily. 

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