Optics: measuring and testing – Lens or reflective image former testing – For optical transfer function
Patent
1992-02-06
1994-02-22
Evans, F. L.
Optics: measuring and testing
Lens or reflective image former testing
For optical transfer function
G01B 900
Patent
active
052892549
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process and an apparatus for testing optical components or systems which are contained in a focusing optical system and a space-resolving light detector close to the focal plane thereof.
Such processes and apparatuses are known. They represent a modification of Hartmann objective testing, and make use of a parallel light beam which illuminates the entire aperture. From this, one or more narrowly delimited beams are masked out by a perforated diaphragm with one perforation or, in the case of multiplex processes, a plurality of encoded perforations, and thus the entire aperture is scanned.
In this case, the difficulty resides in the presentation of a very precise parallel light beam with a plane wavefront over a large cross section; this demands at least a very high expenditure on optical means.
The object of the invention is to provide a process of the type described and an apparatus which manages without large-scale parallel light beams, and permits a compact, robust and relatively economical construction, even for large apertures.
For a process of the type described, the object is achieved in that a source, containing a collimator, for a narrowly delimited precisely parallel light beam with a plane wavefront is moved rectilinearly in a plane parallel to the wavefront. At a plurality of positions of the source the signal of the light detector is determined. Tilting movements of the source perpendicular to the line direction are detected by an apparatus with a second collimator and a space-sensitive detector, and the aperture of the optical system is scanned twice with line directions rotated relative to one another through approximately 90.degree.. In addition, an individual line coming close to the axis of rotation is scanned in a position rotated through approximately 45.degree..
Accordingly, the masked-out partial beam of the known method is replaced by a source for only a narrowly delimited parallel light beam with a plane wavefront, which light beam is then moved for scanning over the aperture. In this case, without further measures, the source for the light beam would ideally have to be moved, free from any tilting, over the surface. However, this requirement can be reduced, by the measures, according to the invention, of a partial measurement of the tilting and an averaging of the residual errors by repeated differing scanning movements, to a dimension which can be well controlled by conventional methods.
The invention is explained in greater detail hereinbelow with reference to the drawings. In the drawings:
FIG. 1 shows the diagrammatic construction of a testing apparatus,
FIG. 2 shows, in the partial FIGS. 2a), 2b) and 2c), the individual scanning procedures.
In FIG. 1, a focusing optical system 1 with the aperture d consists of a lens 11 and a testpiece 12, e.g. a lens or an objective. A space-resolving light detector 2, in particular a highly sensitive lateral detector having a spatial resolution in the nanometer range, is disposed at the spacing of the focal length f, which detector is connected to an operating circuit 21. The active surface area of the light detector 2 is of such magnitude that the entire focus light spot of the optical system 1 affected by defects is covered by it. A light source 31, in particular a laser diode, is combined with a highly corrected collimator 32 and a beam splitter 33 to form a source 3 for a narrowly delimited beam of parallel light with a plane wavefront and disposed on a positioning platform 41. This source 3 directs the parallel light beam, deflected at right angles by the beam splitter 33, having a diameter of, for example, 1 mm, onto the optical system 1, with a wavefront which is planed to an accuracy of one percent of the wavelength.
The positioning platform 41 is movable linearly on a precision positioning device 4 in two orthogonal directions (u,v) and rotatable about an axis (.phi.) perpendicular thereto. A device 42 effects the positioning movements and position reporting for all three axes (u,v,.phi.). As regards the ax
REFERENCES:
patent: 3832066 (1974-08-01), Cornsweet
patent: 4007990 (1977-02-01), McDevitt, Jr. et al.
patent: 4609818 (1986-09-01), Lennemann et al.
patent: 4815844 (1989-03-01), Schmalfuss et al.
patent: 4822165 (1989-04-01), Schmalfuss et al.
Braunecker Bernhard
Gaechter Bernhard
Huiser, deceased Andre
Evans F. L.
Leica Heerbrugg AG
LandOfFree
Process and apparatus for testing optical components or systems does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and apparatus for testing optical components or systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and apparatus for testing optical components or systems will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-175804