Technique for illuminating a surface with a gradient intensity line of light to achieve enhanced two-dimensional imaging

• US 5,097,516 A
• Filed: 02/28/1991
• Issued: 03/17/1992
• Est. Priority Date: 02/28/1991
• Status: Expired due to Fees

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T, Inc.
• Inventors: Amir, Israel
• Primary Examiner(s): Moore, David K.
• Assistant Examiner(s): Couso, Jose L.
• Application Number:
  US07/662,583
• Time in Patent Office: 383 Days
• Field of Search: 382/1, 382/8, 382/30, 382/34, 382/48, 382/65, 382/67, 358/101, 358/106, 358/107, 356/376, 356/383, 356/357, 356/358, 356/363, 356/370, 356/371, 356/372, 250/572, 250/573, 250/550, 250/236
• US Class Current: 382/274
• CPC Class Codes: G01N 2021/95646 Soldering
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G06V 10/145 Illumination specially adapted for pattern recognition, e.g. using gratings
• CPC Class Codes: G06V 10/147 Details of sensors, e.g. sensor lenses fingerprint or palmprint sensors G06V40/13; vascular sensors G06V40/145; eye sensors G06V40/19

Abstract

To obtain an enhanced two-dimensional image of a raised, light-reflective reflective feature (12), and its lower height surrounding background such that the contrast between them is enhanced, a line of light having a gradient profile is directed at an acute angle at the feature and its background to illuminate a strip of area thereacross. The reflectance intensity of the illuminated strip will vary in accordance with the height thereof because of the gradient intensity profile of the line of light. When the line of light is spanned across the feature and its background, the resultant image of the feature and its background, captured by spanning a linescan camera (24) thereacross, will exhibit an enhanced contrast between the feature and its background because of the greater height of the feature.

Claims

1. A method for obtaining a two-dimensional image of a light-reflective topological feature, which is of a different height from a surrounding background, such that the contrast between the feature and its surrounding background is enhanced, comprising the steps of:

generating a line of light, having a gradient intensity profile across its width;

directing the line of light, with its gradient intensity profile, at a light-reflective feature and a surrounding background, which is of a different height, to illuminate a thin strip of area running thereacross such that the intensity of the light striking the feature and its surrounding background varies proportionally with their respective height;

capturing the image of the illuminated strip with a linescan camera;

processing the captured image to detect the intensity of the light reflected therefrom; and

spanning the feature and its surrounding background with the line of light and the linescan camera so that a two-dimensional image thereof is obtained so that the contrast between the feature and its surrounding background is enhanced.

2. The method according to claim 1 wherein the line of light is generated by the steps of:

directing a beam of light into a circle-to-line converter to produce a line of light;

placing an opaque object a spaced distance from circle-to-line converter to partially obstruct the line to alter its intensity from being generally uniform to now being gradient in nature.

3. The method according to claim 1 further including the step of adjusting the gradient profile of the line-of-light by varying the ratio of the distance between the opaque object and the circle-to-line- converter to the distance between the wedge and the feature being illuminated.

4. Apparatus for obtaining a two-dimensional image of a light-reflective feature and a surrounding background which is of a different height such that the contrast within the image between the feature and its background is enhanced, comprising:

means for generating a line of light having a gradient intensity profile across its width;

means for directing the line of light with its gradient intensity profile at an acute angle at a feature and a surrounding background, which is of a different height, to illuminate a strip of area thereon such that the intensity of the light reflected from the strip is proportional to its height;

means for capturing the image of the strip illuminated by the line of light;

means for processing the captured image to detect the intensity of the light reflected from the strip illuminated by the line of light; and

means for spanning the feature and its surrounding background with the line of light and with the image-capturing means to enable a two-dimensional image of the feature and its surrounding background to be obtained such that the contrast between the feature and its surrounding background is enhanced.

5. The apparatus according to claim 4 wherein the means for directing the line of light comprises:

a light source for producing a light beam;

a circle-to-line converter for converting the light beam into a line of light; and

an opaque wedge placed in front of the circle-to-line converter to partially obstruct the line of light to thereby causing its intensity profile to be gradient in nature.