Automatic focusing apparatus
AssigneeTokyo Shibaura Denki Kabushiki Kaisha
InventorsMasana Minami, Tomohide Watanabe
Life of this patent
Estimating the term…
Abstract
An automatic focusing apparatus includes a lens for leading a laser beam onto a sample surface at a predetermined incident angle, a beam splitter to divide the reflected beam from the sample surface in accordance with the vertical shift thereof, a pair of photo diodes to respectively receive the divided beams and produce electric signals, a differential amplifier to produce a differential signal between the electric signals and a mechanism to vertically shift the stage by means of the differential signal to automatically focus a lens system on said sample surface.
Claims15
An automatic focusing apparatus for focusing a lens system for the observation of a sample placed on a stage on the surface of said sample, comprising:
- a collimated beam source;
- an incident optical means for leading a collimated beam from said collimated beam source to said sample surface at a predetermined inclined incident angle in an incident pattern, said incident pattern having a flattened shape;
- photosensitive means to produce an electric signal corresponding to the intensity of light received;
- a reflection optical means for receiving the collimated beam reflected from said sample surface, said reflection optical means including an imaging lens means for imaging an image of said incident pattern on said photosensitive means;
- a detecting means for detecting a shift distance of said sample in the direction of the thickness thereof by means of the electric signal from said photosensitive means and for producing a signal corresponding to said shift distance;
- and shift means for shifting said stage in the direction of the thickness of said sample by means of a signal from said detector means to focus said lens system on said sample surface, wherein said automatic focusing apparatus is optically separate from said lens system.
An automatic focusing apparatus for focusing a lens system onto the surface of a sample placed on a stage, comprising:
- a laser beam source;
- incident optical means for forming an optical pattern of light from a laser beam received from said laser beam source and for directing said optical pattern onto the surface of said sample, said optical pattern of light having a flattened shape, said optical pattern being incident on the surface of said sample at a predetermined angle of incidence, said predetermined angle of incidence lying between 3.degree. and 10.degree. relative to the surface of said sample;
- photosensitive means for producing an electric signal which corresponds to the intensity of light received by said photosensitive means;
- reflection optical means for receiving the optical pattern of light reflected from the surface of said sample and for forming an image of said reflected optical pattern on said photosensitive means;
- detector means coupled to receive the electric signal from said photosensitive means for detecting a shift in position of said sample in the direction of thickness of said sample and for producing a signal proportional to the amount of said shift in position;
- and
- means for moving said stage in the direction of thickness of said sample under control of said signal from said detector means;
- wherein the surface of said sample is maintained at a constant distance from said lens system such that the focus of said lens system onto the surface of said sample is automatically maintained, said automatic focusing apparatus being optically separate from said lens system.
Dependencies are inferred from the claim text.