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AssigneeU.S. Philips Corporation
InventorsJan E. van der Werf, Marinus A. van den Brink, Henk F. D. Linders, Johannes M. M. Beltman
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An imaging apparatus has an imaging system (PL) and a focus detection device for determining a deviation between the image plane of the imaging system and a second plane (WS) on which imaging is to take place. The focus error detection system includes a radiation source (S) which supplies a beam (b.sub.f) having a wide wavelength band, an object grating (G.sub.1) and an image grating (G.sub.2) which are imaged onto each other via the second plane. In the focus detection system a reference beam (b.sub.r) which is reflected by the outer surface (RP) of the imaging system can be used in combination or not in combination with the wideband beam and the gratings. By using a number of such focus detection systems a tilt detection device can be realized for detecting the position of the second plane (WS) with respect to the image plane.
An imaging apparatus comprising an imaging system and an opto-electronic focus detection system for determining a deviation between the image plane of the imaging system and a second plane on which imaging is to take place, said focus detection system comprising a radiation source for supplying a focus detection beam, a radiation-sensitive detector arranged at the same side of the second plane as the radiation source, and optical elements for directing the focus detection beam onto the second plane at a small angle to said plane for changing the vergency of said beam and of that of the beam reflected by the second plane and for directing the last-mentioned beam onto the detector, characterized in that the focus detection beam has a wide wavelength band and in that a first and a second grating are provided, the first grating being arranged in the radiation path between the radiation source and the second plane and the second grating being arranged between said second plane and the detector.
An imaging apparatus comprising an imaging system and an opto-electronic focus error detection system for determining a deviation between the image plane of the imaging system and a second plane on which imaging is to take place, said focus error detection system comprising a radiation source for supplying a focus detection beam, a radiation-sensitive detector arranged at the same side of the second plane as the radiation source, and optical elements for directing the focus detection beam onto the second plane at a small angle to said plane for changing the vergency of said beam and of that of the beam reflected by the second plane and for directing the last-mentioned beam onto the detector, characterized in that a reference beam is provided which is directed onto a surface of the imaging system located opposite the second plane and extends at a small angle to said surface, and a second detector arranged in the path of the reference beam reflected by the surface, a first and a second grating being arranged in the path of the reference beam, and the optical means arranged between the first grating and the second grating for directing and changing the vergency being common for the two beams.
Dependencies are inferred from the claim text.