Topography measuring apparatus

A contour measuring apparatus to measure the three-dimensional contour of a surface, comprising:

• a contour measuring structure having a multi-point light source to direct a plurality of individual light beams each corresponding to individual light points of the multi-point light source onto the surface being measured;
• a photodetector receiving reflections of the individual light beams from said surface for generating electrical output signals corresponding to electro-optically measurable optical images, each of said images corresponding to one of said light points;
• means disposed between said surface being measured and said photodetector for focusing the reflected beams of light from the surface being measured onto the photodetector to form the measurable optical images;
• said focusing means comprising a lens centered on an optical axis extending through said contour measuring structure;
• means between the focusing means and said photodetector for limiting the cone angle of the rays of the individual light beams reflected from the surface whereby each of said reflected rays closely approximates a telecentric principal ray corresponding to a light point;
• said photodetector including a photodetector surface into which said reflected light beams are focused, said photodetector surface being disposed transverse to said optical axis;
• means receiving said electrical output signals from said photodetector for measuring the position of each optical image in the photodetector and for determining both the local radius of curvature of the measured surface at each point of incidence of the individual corresponding light beams and the average radius of curvature of the measured surface;
• and
• calibration means for reducing instrument errors of the apparatus, said calibration means including:
• a calibration surface with a known contour to be positioned in substitution of said surface being measured;
• and
• means for determining the magnification of said lens whereby the curvature of the measured surface can be determined.

A contour measuring apparatus to measure the three-dimensional contour of a surface, comprising:

• a contour measuring structure having a multi-point light source to direct a plurality of individual light beams each corresponding to individual light points of the multi-point light source onto the surface being measured, said surface being the anterior surface of a cornea;
• a photodetector receiving reflections of the individual light beams from said surface for generating electrical output signals corresponding to electro-optically measurable optical images, each of said images corresponding to one of said light points;
• means disposed between said surface being measured and said photodetector for focusing the reflected beams of light from the surface being measured onto the photodetector to form the measurable optical images, said focusing means comprising a lens centered on an optical axis extending through said contour measuring structure;
• means between the focusing means and said photodetector for limiting the cone angle of the rays of the individual light beams reflected from the surface whereby each of said reflected rays closely approximates a telecentric principal ray corresponding to a light point;
• means receiving said electrical output signals from said photodetector for measuring the position of each optical image in the photodetector and for determining both the local radius of curvature of the measured surface at each point of incidence of the individual corresponding light beams and the average radius of curvature of the measured surface;
• a laser-sculpturing apparatus having an axis of sculpturing laser-beam delivery;
• a beam splitter disposed so as to place the axis of laser-beam delivery in coincidence with the optical axis through said contour measuring structure so that said laser-sculpturing apparatus and said contour-measuring structure are interconnected for combined individual laser-sculpting and cornea-evaluation operations.

The method of measuring a surface, comprising the steps of:

• directing a plurality of individual light beams each corresponding to individual light points of a multi-point light source onto the surface being measured;
• providing a photodetector for generating electrical output signals corresponding to electro-optically measurable optical images;
• focusing the reflected beams of light from the measured surface onto the photodetector to form measurable optical images, each of said images corresponding to one of each light points, said step of focusing the reflected beams of light including the steps of:
• disposing a lens transverse to an optical axis extending from said surface being measured to said photodetector;
• directing the beams of light through said lens;
• limiting the cone angle of the reflected beams of light whereby each individual beam closely approximates a telecentric principal ray of individual beam;
• measuring the position of each optical image on the photodetector from the electrical output signals of the photodetector for determining both the local radius of curvature of the measured surface at each point of incidence of the individual light beams and average radius of curvature of the measured surface;
• and
• prior to the step of determining the radius of curvature of the measured surface, reducing the instrument errors of the apparatus using the following steps:
• substituting the surface to be measured with a calibration surface having a known contour;
• and
• determining the magnification of the lens whereby the curvature of the measured surface can be determined.

The method of measuring the three-dimensional contour of the surface of a cornea, comprising the steps of:

• providing a multi-point light source;
• directing a plurality of individual light beams each corresponding to individual light points of a multi-point light source onto the corneal surface being measured, said surface being the anterior surface of a cornea;
• providing a photodetector for generating electrical output signals corresponding to electro-optically measurable optical images;
• focusing the reflected beams of light from the corneal surface being measured onto the photodetector along an optical axis extending from the measured surface to the photodetector to form the measurable optical images, each of said images corresponding to one of said light points;
• limiting the cone angle of the rays of the individual light beams reflected from the surface whereby each of said reflected rays closely approximates a telecentric principal ray corresponding to a light point measuring the position of each optical image on the photodetector from the electrical output signals of said photodetector for determining both the local radius of curvature of the measured corneal surface at each point of incidence of the individual corresponding light beams and the average radius of curvature of the measured surface;
• providing a laser-sculpturing apparatus having an axis of sculpturing laser-beam delivery for laser sculpturing of corneas;
• disposing a beam splitter so as to place the axis of laser-beam delivery in coincidence with the optical axis from the measured surface to the photodetector for combined individual laser-sculpting and cornea-evaluation operations.