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EP0079439A1 Expired / Lapsed EP ⏱️ 0.0 years remaining

Optical system for oblique viewing

Assignee: International Business Machines Corp
•
Filing: 1982-09-08
•
Granted: —
•
Expires: 2002-09-08
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Abstract

Abstract An optical system (10) for the oblique viewing of an object (20) includes a specific embodiment for quantitatively determing the volume of solder mounds (22) on chips (20) and wafers without the introduction of keystone distortion and anamorphosis. The optical system (10) includes means (26) for directing an image of the solder mounds (22) at an angle (8 3 ) to a diffraction grating (28) to provide a diffracted beam (30) normal to the grating (28). The diffracted beam (30) is then processed in a conventional manner to yield the sought-after information. In a preferred embodiment the directing means is an afocal lens system having a magnification of one.

Inventors

  • 👤 Jean Claude Andre Chastang
  • 👤 Robert Frederick Koerner

Bibliographic Details

Application Number —
Jurisdiction EP
Data Source google_patents
Last Synchronized 2026-11-05 09:30
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/42; G02B27/4205; G01; G01B; G01B11/00

Claims Analysis

Total Claims: 8
Claim 1
Independent Claim 66 words
Optical system for projecting an image of an object (20) that is inclined to the optical axis (25) by a first angle (θ 2 ) characterized in that an imaging system (26) first projects an image onto a diffraction grating (28) that is inclined to the optical axis by a second angle (θ 3 ) and that the image diffracted normal to the grating is observed.
Claim 2
Dependent Claim 66 words
Optical system for projecting an image of an object (20) that is inclined to the optical axis (25) by a first angle (θ 2 ) characterized in that an imaging system (26) first projects an image onto a diffraction grating (28) that is inclined to the optical axis by a second angle (θ 3 ) and that the image diffracted normal to the grating is observed.
Claim 3
Dependent Claim 24 words
Optical system according to claim 1, characterized in that the imaging system (e.g. lens 26) has a magnification of an absolute value of one.
Claim 4
Dependent Claim 49 words
Optical system according to claim 1 or 2, characterized in that the tilted grating (28) has a period a = X/sin θ 3 where λ is the wavelength of the diffracted beam and 8 3 is the angle included between the optical axis and the normal to the grating.
Claim 5
Dependent Claim 49 words
Optical system according to one of the claims 1 to 3, characterized in that the object (20) is illuminated under oblique incidence (angle 8 1 ) and that the impinging light beam (14) and the optical axis (25) are opposite with respect to the normal to the object surface.
Claim 6
Dependent Claim 19 words
Optical system according to claim 4, characterized in that specularly reflected light is used for imaging the object (20).
Claim 7
Dependent Claim 35 words
Optical system according to one of the claims 1 to 5, characterized in that a light detector (34) is used which is equipped to analyse the contrast in the image of the projected diffracted beam.
Claim 8
Dependent Claim 27 words
Optical system according to one of the claims 1 to 6, characterized in that the object (20) is a semiconductor device with solder mounds on its surface.

References Cited (Backward Citations)

US3861801A Cited
US4272196A Cited

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