Digital image capture apparatus and method for obtaining a digital image of an object

• US 7,619,664 B2
• Filed: 10/13/2005
• Issued: 11/17/2009
• Est. Priority Date: 02/16/2001
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Pollard, Stephen B., Pilu, Maurizio
• Primary Examiner(s): Villecco; John M
• Application Number:
  US11/248,156
• Publication Number:
  US 20060033835A1
• Time in Patent Office: 1,496 Days
• Field of Search: 348/77, 348/78, 348/239, 348/241, 348/246, 348/370, 348/371, 382/117, 382/264, 382/274, 382/275, 358/450, 358/475, 358/509, 351/207
• US Class Current: 348/241
• CPC Class Codes: H04N 1/00835 Detecting external or ambient light
• CPC Class Codes: H04N 1/2112 using still video cameras
• CPC Class Codes: H04N 1/2116 Picture signal recording combined with imagewise recording, e.g. photographic recording photographic cameras G03B19/00

Abstract

A digital image capture apparatus is provided which is arranged to capture at least two images of a document and combine the images to produce a final image in which the effects of specular reflection and/or ambient light are removed. The apparatus includes a light source and a first image is captured with the source illuminating the document. A second ambient image is captured with the light source switched off, and the images are combined either by subtracting the ambient image from the first image or by replacing areas of the first image by corresponding areas of the ambient image.

Claims

1. A digital image capture apparatus configured to capture an image of a document at least partially illuminated by ambient light, the apparatus comprising:

a digital camera positioned vertically above said document, said digital camera comprising;

a lens;

a detector element located proximate to said lens, wherein said detector element comprises an array of image collecting nodes which each produce an output signal;

an illumination source for illuminating said document, wherein said illumination source is positioned proximate to said lens and is configured to emit a controlled beam of light at an angle in a direction of said document; and

a detector read-out circuit, wherein said detector read-out circuit is configured to produce a captured image corresponding to said output signals received from said image collecting nodes, and

a computing device electronically coupled to the digital camera, said computing device comprising;

a controller configured to control said detector read-out circuit and said illumination source, wherein said controller is configured to provide a first control signal to said detector read-out circuit to capture a first image of said document when illuminated by said illumination source at a first intensity and by said ambient light to produce said first image, and wherein said controller is further configured to provide a second control signal to said detector read-out circuit to capture a second image of said document when said document is illuminated by said illumination source at a second, lower, intensity and by said ambient light, said second, lower, intensity having a value greater than or equal to zero intensity but less than the first intensity; and

a processor configured to process said first image with said second image to produce a final image of said document, wherein said processor is configured to process said first image with said second image to produce said final image by subtracting a value at each data point in said second captured image from a value at each corresponding data point in said first captured image to arrive at a final value for each data point, wherein said processor is configured to allocate said final value for each data point to a corresponding data point in said final image.

2. Apparatus according to claim 1 wherein said first image and said second image are captured with substantially a same exposure.

3. Apparatus according to claim 2 wherein said processor includes a low pass filter, and wherein at least one of said captured images is passed through said low pass filter prior to subtraction.

4. Apparatus according to claim 3 wherein only said second captured image is low-pass filtered.

5. A method of capturing an image of a document at least partially illuminated by ambient light, said method comprising

capturing a first image of said document with a light source illuminating said document at a first intensity, wherein said light source is part of a digital camera positioned vertically above said document, wherein said light source is positioned proximate to a lens and is configured to emit a controlled beam of light at an angle in a direction of said document;

capturing a second image of said document with said light source illuminating said document at a second, lower, intensity, wherein said first image and said second image are captured using identical exposures; and

processing, at a computing device electronically coupled with the digital camera, said first captured image with said second captured image to produce a final image of said document, wherein said second lower intensity is greater than or equal to zero intensity but less than said first intensity,

wherein said processing said first captured image with said second captured image to produce a final image comprises;

subtracting a value at each data point in said second captured image from a value at each corresponding data point in said first captured image to arrive at a final value for each data point; and

allocating said final value for each data point to a corresponding data point in said final image.

6. A digital image capture apparatus configured to capture an image of an object at least partially illuminated by ambient light, the apparatus comprising:

a digital camera positioned vertically above said object, said digital camera comprising;

a lens;

a detector element located proximate to said lens, wherein said detector element comprises an array of image collecting nodes which each produce an output signal;

an illumination source for illuminating said object wherein said illumination source is positioned proximate to said lens and is configured to emit a controlled beam of light at an angle in a direction of said object; and

a detector read-out circuit, wherein said detector read-out circuit is configured to produce a captured image corresponding to said output signals received from said image collecting nodes, and

a computing device electronically coupled to the digital camera, said computing device comprising;

a controller configured to control said detector read-out circuit and said illumination source, wherein said controller is configured to provide a first control signal to said detector read-out circuit to capture a first image of said object when illuminated by said illumination source at a first intensity and by said ambient light to produce said first image, and wherein said controller is further configured to provide a second control signal to said detector read-out circuit to capture a second image of said object when said object is illuminated by said illumination source at a second, lower, intensity and by said ambient light, said second, lower, intensity having a value greater than or equal to zero intensity but less than the first intensity; and

a processor configured to process said first image with said second image to produce a final image of said object, wherein said processor is configured to process said first image with said second image to produce said final image by subtracting a value at each data point in said second captured image from a value at each corresponding data point in said first captured image to arrive at a final value for each data point, wherein said processor is configured to allocate said final value for each data point to a corresponding data point in said final image.

7. A digital image capture apparatus configured to capture an image of a document at least partially illuminated by ambient light, the apparatus comprising:

a digital camera positioned vertically above said document, said digital camera comprising;

a lens

a detector element located proximate to said lens, wherein said detector element comprises an array of image collecting nodes which each produce an output signal;

an illumination source for illuminating said document, wherein said illumination source is positioned proximate to said lens and is configured to emit a controlled beam of light at an angle in a direction of said document; and

a detector read-out circuit, wherein said detector read-out circuit is configured to produce a captured image corresponding to said output signals received from said image collecting nodes, and

a computing device electronically coupled to the digital camera, said computing device comprising;

a controller configured to control the detector read-out circuit and the illumination source so as to capture a plurality of images at different levels of illumination;

a processor configured to process the plurality of images and produce a final image based thereon, wherein said processor is configured to process said plurality of images to produce said final image by subtracting a value at each data point in a second image comprising only ambient light from a value at each corresponding data point in a first image comprising ambient light and light from the illumination source to arrive at a final value for each data point, wherein said processor is configured to allocate said final value for each data point to a corresponding data point in said final image.

8. A digital image capture apparatus of claim 7, wherein said illumination source is arranged in a predetermined spatial relationship with said digital camera.

9. A digital image capture apparatus of claim 7, wherein said first image and said second image are captured with substantially a same exposure.

10. A digital image capture apparatus configured to capture an image of a object at least partially illuminated by ambient light, the apparatus comprising:

a digital camera positioned vertically above said object, said digital camera comprising;

a lens

a detector element located proximate to said lens, wherein said detector element comprises an array of image collecting nodes which each produce an output signal;

an illumination source for illuminating said object, wherein said illumination source is positioned proximate to said lens and is configured to emit a controlled beam of light at an angle in a direction of said object; and

a detector read-out circuit, wherein said detector read-out circuit is configured to produce a captured image corresponding to said output signals received from said image collecting nodes, and

a computing device electronically coupled to the digital camera, said computing device comprising;

a controller configured to control the detector read-out circuit and the illumination source so as to capture a plurality of images at different levels of illumination;

a processor configured to process the plurality of images and produce a final image based thereon, wherein said processor is configured to process said plurality of images to produce said final image by subtracting a value at each data point in a second image comprising only ambient light from a value at each corresponding data point in a first image comprising ambient light and light from the illumination source to arrive at a final value for each data point, wherein said processor is configured to allocate said final value for each data point to a corresponding data point in said final image.

11. A digital image capture apparatus of claim 10, wherein said first image and said second image are captured with substantially a same exposure.