Auto-focus method for a coordinate-measuring apparatus
AssigneeCarl Zeiss Industrielle Messtechnik GmbH
InventorsDominik Seitz, Nils Haverkamp, Christoph Kranz
Life of this patent
Estimating the term…
Abstract
A method is disclosed for ascertaining a focus image distance of an optical sensor, which is provided with a lens, of a coordinate-measuring apparatus onto a workpiece to be measured, wherein the optical sensor and/or the workpiece are movable in a Z direction such that a distance in the Z direction between the workpiece and the optical sensor is variable. Further, a corresponding coordinate-measuring apparatus and a computer program product are disclosed.
Claims21
A method for ascertaining a focus image distance of an optical sensor of a coordinate-measuring apparatus with respect to a surface of a workpiece to be measured, the optical sensor being provided with a lens, at least one of the sensor and the workpiece being movable in a Z direction such that a distance in the Z direction between the workpiece and the optical sensor is variable, the method comprising at least one of a determination step and an approximation step;
- the determination step including:
- setting a first focal distance and a second focal distance;
- recording a first image of a surface of the workpiece with the optical sensor;
- assessing an intensity of the recorded first image of the surface of the workpiece at the first focal distance;
- recording a second image of the surface of the workpiece with the optical sensor;
- assessing the intensity of the second image of the surface of the workpiece at the second focal distance to determine therefrom a most probable location of a best focus in relation to the first focal distance and to the second focal distance;
- and
- the approximation step including:
- setting at least three different focal distances in a proximity of the most probable location of the best focus;
- and,
- approximately determining a location of the best focus based on the intensities of the recorded images.
The coordinate-measuring apparatus of 19, wherein:
- the illumination system emits light with wavelengths λ in a range of 400 nm≦λ≦650 nm, and
- for at least one wavelength λ in said range for the illumination system for generating the bright-field incident light illumination on the surface to be measured, the lens has a same location of the best focus as for the imaging of the surface to be measured on the sensor.
Dependencies are inferred from the claim text.