Method of and an apparatus for measuring a specimen by means of a scanning probe microscope
The invention relates to a method of and an apparatus for measuring a specimen by means of a scanning probe microscope, especially a scanning force microscope, wherein a probe ( 5 ) is displaced with respect to a specimen ( 6 ) by means of lateral and vertical shifting units ( 1 ) to measure the specimen ( 6 ); measuring light rays ( 21 ) are generated by means of a light source ( 20 ) and directed to a reflection means ( 91 ) disposed on the probe; the measuring light rays ( 21 ) are reflected at the reflection means ( 91 ), whereby reflected measuring light rays ( 21 a ) are formed; and the reflected measuring light rays ( 21 a ) are directed by means of a correction lens ( 47 ) to a detector surface ( 32 ) of a detector means ( 27 ) to generate a measurement signal, the correction lens ( 47 ) being positioned at a distance from the detector surface ( 32 ) substantially corresponding to a focal length of the correction lens ( 47 ).
1. A method of measuring a specimen by means of a scanning probe microscope, comprising the steps of:
displacing a probe with respect to a specimen by means of lateral and vertical shifting units to measure the specimen;
generating measuring light rays by means of a light source and directing the measuring light rays to a reflection means disposed on the probe;
reflecting the measuring light rays at the reflection means, thereby forming reflected measuring light rays; and
generating a measurement signal by directing the reflected measuring light rays by means of a correction lens to a detector surface of a detector means, wherein said step of generating a measurement signal includes positioning the correction lens at a distance from the detector surface substantially corresponding to a focal length of the correction lens; moving the light source, the reflection means, and the detector means along in a lateral direction as the probe is displaced laterally so that the reflection means is maintained relatively at rest with respect to the light source and the detector means, and the reflection means is moved with respect to the light source and the detector means along a vertical direction as the probe is displaced vertically with respect to the specimen.
2. The method as claimed in claim 1 , wherein said step of directing the measuring light rays includes directing the measuring light rays to the detector surface by means of an optical deflection means for deflecting the measuring light rays.
3. The method as claimed in claim 1 , wherein said step of directing the reflected measuring light rays includes directing the reflected measuring light rays to the detector surface by means of a further optical deflection means.
4. The method as claimed in claim 1 , further comprising the step of guiding the measuring light rays in a light path from the light source to the reflection means at least partly along a condenser light path.
5. The method as claimed in claim 1 , further comprising the step of selecting a value of about 30 degrees for an angle of incidence of the measuring light rays with respect to a normal of a reflection surface of the reflection means.
6. The method as claimed in claim 1 , further comprising the step of illuminating the specimen by a condenser light which spreads through a condenser light path.
7. An apparatus for measuring a specimen by means of a scanning probe microscope comprising:
a lateral shifting unit for lateral displacement of a probe with respect to the specimen;
a vertical shifting unit for vertical displacement of the probe with respect to the specimen;
a light source for generating measuring light rays which may be directed along a light path to a reflection means disposed on the probe and for reflecting the measuring light rays at said reflection means so that reflected measuring light rays are formed;
a detector means having a detector surface for generating a measurement signal when the reflected measuring light rays impinge on said detector surface; and
a correction lens for focusing the reflected measuring light rays on said detector surface, said correction lens being positioned at a distance from said detector surface substantially corresponding to a focal length of said correction lens;
said light source, said reflection means, and said detector means being coupled to said lateral shifting unit so as to be moved along, upon lateral displacement of said probe with respect to the specimen, along a lateral direction so that said reflection means is maintained relatively at rest relative to said light source and said detector means, and said reflection means being coupled to said vertical shifting unit such that said reflection means is moved along a vertical direction with respect to said light source and said detector means upon vertical displacement of said probe with respect to the specimen.
8. The apparatus as claimed in claim 7 , further comprising an optical deflection means for guiding the measuring light rays to said reflection means.
9. The apparatus as claimed in claim 7 , further comprising further optical deflection means for guiding the reflected measuring light rays to said detector surface of said detector means.
10. The apparatus as claimed in claim 7 , wherein the light path of the measuring light rays from said light source to said reflection means is formed at least partly along a condenser light path.
11. The apparatus as claimed in claim 7 , wherein a reflection surface of said reflection means is inclined with respect to a central axis of said lateral shifting unit.